home
China    Japan    ametek.com    Home    Contact Us    Careers               
about us
General EBSD Bibliography
What's New
EBSD Technologies
Cool Stuff
 
General EBSD Bibliography - Search By Letter L


Search by Author:     
Search by Article:
A    B    C    D    E    F    G    H    I    J    K    L    M    N    O    P    Q    R    S    T    U    V    W    X    Y    Z   

LA  LE  LI  LL  LO  LU 
173 records found


1.    Lücken, H. and D. Raabe (2002). Orientation Dependence of Recrystallization in Aluminum. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.

The orientation dependence of recrystallization in aluminum (99.99%) was studied by means of experimental methods and computer simulation. Samples with columnar grain morphology were deformed in plane strain compression in a channel die setup up to a technical thickness reduction of 50% in several defined steps. After the last deformation step the samples were recrystallized at different temperatures. After each of the deformation steps and each of the recrystallization steps, the samples were analyzed by means of electron backscattering diffraction. With the orientation data gained from the last deformation step, an input file was generated for a recrystallization simulation based on a probabilistic cellular automation.




2.    Laabs, F. C. and A. M. Russell (2002). Comparison of OIM and XRD Texture Determinations in a Deformation Processed -Ti +Y Metal-Metal Composite. Microscopy and Microanalysis 2002, Québec City, Québec, Canada, Cambridge University Press.




3.    Lahn, L. and K. Kopal (1996). "Description and examples of the use of single grain orientation measurements by the EBSP-method in the SEM." Praktische Metallographie 33(10): 516-30.

An important and challenging aspect of the development of a system for fully automated electron backscattering pattern (EBSP) analysis is the design of reliable digital image processing routines for automatic detection and localisation of the bands in the digitised patterns. Procedures based on the Hough transform which permit precise localisation of a large number of bands in digital EBSPs are described in detail. Special attention is paid to the analysis and post-processing of the the Hough space which ensure a high intensity to noise and a high precision of the measured band positions. The possibilities for further improvements and extensions of the procedures are also discussed, including the possibility of extracting band width information from the Hough transform. To demonstrate these possibilities, a new procedure is outlined and shown to be capable of providing high precision estimates of the EBSP band positions and, in addition, fairly precise estimates of the band widths. (17 References).




4.    Lambert-Perlade, A., A. F. Gourgues, et al. (2004). "Mechanisms and Modeling of Cleavage Fracture in Simulated Heat-Affected Zone Microstructures of a High-Strength Low Alloy Steel." Metallurgical and Materials Transactions A 35A(3A): 1039 - 1053.

The effect of the welding cycle on the fracture toughness properties of high-strength low alloy (HSLA) steels is examined by means of thermal simulation of heat-affected zone (HAZ) microstructures. Tensile tests on notched bars and fracture toughness tests at various temperatures are performed together with fracture surface observations and cross-sectional analyses. The influence of Martensite-Austenite (M-A) constituents and of "crystallographic" bainite packets on cleavage fracture micromechanisms is, thus, evidenced as a function of temperature. Three weakest-link probalistic models (the Master-Curve {MC} approach, the Beremin model, and a "double-barrier" {DB} model) are applied to account for the ductile-to-brittle transition (DBT) fracture toughness curve. Some analogy, but also differences, are found between the MC approach and the Beremin model. The DB model, having nonfitted, physically based scatter parameters, is applied to the martensite-containing HAZ microstructures and gives promising results.




5.    Lambert-Perlade, A., A. F. Gourgues, et al. (2004). "Austenite to bainite phase transformation in the heat-affected zone of a high strength low alloy steel." Acta Materialia 52: 2337-2348.

The austenite to bainite phase transformation was investigated in a low alloy structural steel after simulated welding heat treatment, by means of light microscopy, electron backscatter diffraction and transmission electron microscopy. Upper bainite packets result from the growth of groups of laths having close crystallographic orientations but highly misoriented habit planes. Self-accommodation of the transformation eigenstrain was evaluated for various bainite configurations using a micromechanical model. The observed pairs of variants seem to help limiting plastic strain in the austenite phase, thus enhancing growth of the bainite phase during cooling.




6.    Lan°af, F. J. G., S. C. Paolinelli, et al. (2005). Texture optimization in Non-Oriented Electrical Steels: The Role of the Goss Texture Component. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.

The non-oriented electrical steels, produced with different processing procedures, base their magnetic property improvement mainly on the increase of the Goss component. This paper relates the anisotropy of magnetic properties to texture, describes the texture evolution in both the Fully-processed and the Semi-processed classes of electrical steels.




7.    Lan°af, F. J. G., T. Yonamine, et al. (2001). "Magnetic properties of silicon steel simulating texture of continuous strip casting." 56DG Congresso Anual da ABM Internacional 2001: 12.

Besides its cost reduction potential, the strip casting process allows favorable conditions for obtaining exceptional magnetic properties. The solidification direction for ferritic alloys such as Fe-3.5%Si favors the formation of the ideal (100)<0vw> texture. Nevertheless, this texture is not always obtained in the solidification and, furthermore, cold rolling and annealing alter the texture. This paper shows results of as-cast 3 mm thick strip cast 3.5%Si alloy and compares it to those of directionally solidified sample and to a commercial 2%Si non-oriented fully processed lamination. Unfortunately, the ideal texture was not obtained. The magnetic properties were measured in ring samples milled from the bulk strip and from the directionally solidified cylinder, in the as-milled and in the annealed condition. Rings from the commercial laminations were punched and annealed. To avoid thickness effects magnetic measurements were performed in the quasi-static condition. Dissipated energy per cycle at 1.5T, B50 and H1.7 values were measured and the last two were compared to theoretical values calculated based on the Lawton and Stewart model (1). H1.7 values are not normalized, but allow a better comparison between materials than B50 values. Results are discussed in terms of texture measurements by x-ray and EBSD. A considerable improvement in B50 and H1.7 values in the directionally solidified sample was observed. Dissipated energy per cycle values are not as good as the permeability values, probably due to the high inclusion content of the samples.




8.    Lan, Y., H. J. Klaar, et al. (1992). "Evolution of Dislocation-Structures and Deformation-Behavior of Iron at Different Temperatures.2. Dislocation Density and Theoretical-Analysis." Metallurgical Transactions A 23(2): 545-549.




9.    Lang, A. R. (1995). "Expolitation of N-Beam Dynamical Effects in Pseudo-Kossel Diffraction Patterns of Nearly Perfect Crystals." Journal of Physics D 28(4A): A1-A7.




10.    Lang, A. R. and G. Pang (1995). "A Possible New Route to Precise Lattice-Parameter Measurement of Perfect Crystals Using the Divergent-X-Ray-Beam Method." Journal of Applied Crystallography 28(FEB): 61-64.




11.    Lang, A. R., A. P. W. Makepeace, et al. (1997). "Combining Optical Microscopy, X-Ray Microradiography and X-Ray Topography in the Study of Individual CVD Diamond Crystallites." Diamond and Related Materials 6(9): 1226-1230.




12.    Langdon, T. G. (1981). "Observations on the Magnitude of Grain-Boundary Sliding in Region-1 of Superplasticity." Journal of Materials Science 16(9): 2613-2616.




13.    Langdon, T. G. (1981). "The Significance of Grain-Boundary Sliding in Creep and Superplasticity." Metals Forum 4(1-2): 14-23.




14.    Langdon, T. G. (1982). "The Mechanical-Properties of Superplastic Materials." Metallurgical Transactions A 13(5): 689-701.




15.    Langdon, T. G., T. R. McNelley, et al. (2004). "Texture and microstructural evolution in pure aluminum during high-pressure torsion." JOM 56(11): 279.

An orientation imaging microscopy (OIM) investigation was conducted to evaluate the microstructural characteristics in samples of pure aluminum processed by high-pressure torsion (HPT) under both constrained and unconstrained conditions. Electron backscattering diffraction (EBSD) techniques were employed to measure the microtextures and the distributions of the misorientation angles. A thorough analysis of the microtexture has revealed the shear plane normal and direction for aluminum specimens. This paper discusses the common features of the texture components by comparison with aluminum deformed by equal-channel angular pressing. It is shown that the magnitude of the grain refinement depends upon the location in the HPT disc and the pressing conditions.




16.    Langdon, T. G., T. R. McNelley, et al. (2006). Microstructure evolution in commercial purity aluminum during high-pressure torsion. 2006 TMS Annual Meeting, San Antonio, Texas, USA.

An investigation was conducted to evaluate the microstructural evolution occurring in disks of commercial purity aluminum processed by high-pressure torsion (HPT) under constrained conditions. Microhardness measurements were taken to assess the variation in hardness across the diameters of disks subjected to different imposed strains and the microstructures were observed at the edges and in the centers of the disks using transmission electron microscopy. The results show the microhardness is lower and there is less grain refinement in the central regions of the disks in the initial stages of torsional straining but the microstructures become reasonably homogeneous across the disks at high-imposed strains. A comparison with the results of an OIM study of ECAP aluminum is also presented.




17.    Langer, E., R. Kurt, et al. (1999). "Kopsko - A Computer-Program for Generation of Kossel and Pseudo-Kossel Diffraction Patterns." Crystal Research and Technology 34(7): 801-816.




18.    Langer, E., S. Dabritz, et al. (1998).  "Investigation of Divergent Beam X-Ray Reflex Sections Especially Indication by Computer-Simulation and Assignment to the Grains in Polycrystalline Samples." Fresenius Journal of Analytical Chemistry 361(6-7): 728-732.




19.    Lapasset, G., Y. Girard, et al. (2003). Investigation of the Microstructure and Properties of a Friction Stir Welded Al-Mg-Sc Alloy. Thermec' 2003, Leganés, Madrid, Spain, Trans Tech Publications Ltd.

The objective of this study is to provide a better knowledge of the relationships between microstructural evolution and both mechanical and corrosion properties of a friction stir welded Al-Mg-Sc alloy. Microstructures were studied by optical microscopy, transmission electron microscopy, electron backscattered diffraction and microhardness measurements. Tensile testing was carried out in order to determine the global behavior of the joint as well as the local behavior of the main zones of the joint. The weld nugget appears to be the softest zone of the weld. Its undermatching is analyzed with reference to the various hardening contributions of relevance in Al-Mg-Sc alloys. It is tentatively concluded that recrystallization which occurred in the nugget at the expense of the fine unrecrystallized structure of the base metal is primarily responsible for the loss of strength in the joint. Accelerated corrosion tests did not show any evidence of susceptibility to intergranular attack.




20.    Larsen, A. W. and D. J. Jensen (2003). "Automatic determination of recrystallization parameters in metals by electron backscatter pattern line scans." Materials Characterization 51(4): 271-282.

In this paper, a new automatic procedure for determining critical recrystallization parameters, which are important when studying recrystallization kinetics, is presented. The method is based on electron backscatter patterns (EBSP) line scans using a scanning electron microscope, where three parallel lines are scanned. The concepts of equivalence and connectivity are used to group the data points into those originating in recrystallized grains and those originating in the deformed matrix. The computer program implementing the automatic procedure is tested in three different ways: three short scans are performed, where the calculations are also done by hand; the results of two long scans are compared to the direct observation of the microstructure seen in orientation image maps (OIMs), and the results of scans from a series of samples are compared to statistical results obtained manually. A good correlation was achieved in all three cases.




21.    Larsen, A. W., C. Gundlach, et al. (2004). In Situ Investigation of Bulk Nucleation by X-Ray Diffraction. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.




22.    Lartigue, S., O. Khalfallah, et al. (1982). "Extrinsic Dislocations, Intergranular Segregation and Grain-Boundaries Mobility." Revue de Physique Appliquee 17(10): 649-656.




23.    Lassila, D. H., A. Goldberg, et al. (2002). "The Effect of Grain Boundaries on the Athermal Stress of Tantalum and Tantalum-Tungsten Alloys." Metallurgical and Materials Transactions A 33A(11): 3457-3464.

The temperature dependence of the yield stress of polycrystalline Ta, Ta-2.47 w pct W (Ta-2.5W), and Ta-9.80 wt pct W (Ta-10W) was measured to study the effect of grain boundaries and tungsten concentration on athermal strength components. Compression tests were performed over a temperature range from 77 to 1223 K at strain rates of 10-4 and 10-1 s-1, The test results show that the yield stress of Ta becomes independent of temperature above about 400 K, indicating an "athermal" regime. In contrast, the temperature dependence of yield stress was still significant for Ta-10W up to the maximum test temperature. An analysis of the test data using single-crystal data in conjunction with Taylor factors was performed to assess the effect of grain boundaries on the athermal component of flow stress at 600 K. The results indicated that the long-range athermal stress at the yield point due to grain boundaries is approximately 13 - 41 MPa for the study materials and decreases with an increase in tungsten concentration. These results are discussed with regards to constitutive modeling of flow stress.




24.    Lassila, D. H., A. J. Schwartz, et al. (1997). Mechanical Behavior of Tantalum and Tantalum-Tungsten Alloys: Texture Gradients and Macro/Micro-Response. U. S. Army Symposium on Solid Mechanics, Myrtle Beach, South Carolina.

We have examined the mechanical response of unalloyed tantalum and tantalum-tungsten alloy annealed plates over a wide range of loading conditions. In general, we have observed that unalloyed tantalum exhibits non-uniform mechanical behavior, for example, hourglassing of compression samples and multiple instabilities during tensile deformation. In contrast, the tantalum-tungsten alloys do not exhibit any unusual non-uniform behavior. In this work, we present data revealing the spatial distribution of texture in unalloyed tantalum and tantalum-tungsten alloys. Significant variations in texture both through the thickness and from one area of the plate to another were found to be characteristic of the unalloyed tantalum. The dominant feature of the texture variations was found to be enhanced <111> crystal direction fractions at the center of the plate, with a decreasing fraction near the surface. We find that the variation in texture in the tantalum-tungsten alloys is substantially less than that seen in the unalloyed tantalum with primarily a <100> cube texture throughout. This study suggests that the texture gradients are responsible for the non-uniform mechanical response of unalloyed tantalum and that the uniform behavior of the tantalum-tungsten alloys is a consequence of the absence of texture gradients.




25.    Last, H. R., K. J. Hemker, et al. (2000). "MEM Material Microstructure and Elastic Property Research."




26.    Lavigne, O., C. Ramusat, et al. (2004). Relationships between microstructural instabilities and mechanical behaviour in new generation nickel-based single crystal superalloys. Superalloys 2004. Proceedings of the Tenth International Symposium on Superalloys sponsored by the TMS Seven Springs International Symposium Committee, in Cooperation with the TMS High Temperature Alloys Committee and ASM International, Champion, Pennsylvania, USA, TMS.

Microstructural instabilities occurring in two new generation single crystal nickel-based superalloys containing additions of both Re and Ru have been characterised by means of electron backscatter diffraction (EBSD). Cellular colonies develop in the MC632 experimental alloy at subgrain boundaries with misorientations higher than 10°. The role of these microstructural instabilities in the mechanical behaviour was investigated. After creep at high temperature microcracks are observed at the limit of the cellular colonies but these defects are not more frequent than those initiating from micropores or within the dendrites. As only a low volume fraction of gamma - gamma *prime; alloy is involved in this transformation, the influence of this phenomenon on the alloy creep strength is negligible. Secondary reaction zones (SRZ) were observed beneath Pt-modified aluminide coating in the MC544 superalloy. EBSD analysis clearly demonstrated the polycrystalline structure of these SRZ. Despite the presence of internal grain boundaries, the SRZ are not preferential sites for premature failure initiation. However, the stress-rupture life is adversely affected by the reduction of the load-bearing section of safe gamma - gamma *prime; alloy. The decrease of low cycle fatigue (LCF) strength observed at 650° C for coated MC544 compared to the bare alloy was mainly attributed to premature crack initiation within the aluminide coating and not from the SRZ. During LCF tests at 950° C of coated MC544, numerous cracks also initiate from the aluminide coating but then remain restricted to the SRZ area. The failure initiates at internal casting porosities. The slight LCF strength reduction observed in these conditions was attributed to the load bearing section reduction of unaffected gamma - gamma *prime; alloy.




27.    Lavrentyev, F. F. (1980). "The Type of Dislocation Interaction as the Factor Determining Work-Hardening." Materials Science and Engineering 46(2): 191-208.




28.    Le Gall, R. and J. J. Jonas (2000). Effects of Solutes on Kinetics, Grain Size and Texture During the Dynamic Recrystallization of Nickel. Thermec 2000, Las Vegas, Nevada, USA, Elsevier Science Ltd.

Solute effects during dynamic recrystallization (DRX) were studied using 5 different nickel-sulphur alloys containing from 1 to 20 ppm of sulphur. At a given temperature and strain rate, the steady state stress for dynamic recrystallization, measured using hot compression tests, depends only on the sulphur concentration. The experimental results were analysed using a model that relates the steady state stress to the grain boundary (GB) mobility. At the lower temperatures, the mobilities are strongly reduced by a solute drag effect; above a transition temperature, the drag effect becomes negligible. The grain sizes and GB character distributions (GBCD’S) were measured after compression testing usig both optical microscopy and orientation imaging microscopy (OIM). A model taking into account the reduction of the mobility of random GB’s due to sulphur segregation and the occurrence of twinning is proposed to account for the steady state grain size during DRX. The GBCD’S are discussed in terms of GB selection as a consequence of solute drag and of the competition between twinning and GB displacement. The effect of solutes on the stacking fault energy (SFE) is taken into account using the Suzuki mechanism, which predicts a decrease in SFE due to solute segregation.




29.    Leach, C. (2001). "Crystal plane influence of the EBIC contrast in zinc oxide varistors." Journal of the European Ceramic Society 21: 2127-2130.

Scanning electron microscopy (SEM) based remote electron beam induced current (REBIC) microscopy has been used to investigate the electrical characteristics of individual grain boundaries in a zinc oxide based varistor. Although some grain boundaries showed ‘bright and dark’ contrast consistent with symmetrical, opposed, electric fields on either side of a charged grain boundary, the majority of interfaces were found to be electrically asymmetric showing only either bright or dark contrast. In these cases, the application of an external voltage bias across the grain boundary of several 100s of mV was necessary to restore the symmetrical structure. The orientations of grains on either side of grain boundaries showing each of these contrast types were determined using electron backscattered diffraction (EBSD) analysis and the grain boundary plane orientation was established using depth resolved EBIC. It was found that the asymmetry in the electrical structure is governed by the orientations of the grain boundary planes on either side of the interface, demonstrating some crystallographic control of the electrical character of the barrier structure.




30.    Leach, C. (2001). "Crystallographic control of the barrier structure in zinc oxide varistors." International Journal of Inorganic Materials 3: 1117-1119.

Scanning electron microscope (SEM) based remote electron beam induced current (REBIC) microscopy has been used to investigate the electrical characteristics of individual grain boundaries in a zinc oxide based varistor. Although some grain boundaries showed the expected ‘bright and dark’ contrast consistent with symmetrical, opposed, electric fields on either side of a charged grain boundary, the majority of interfaces are electrically asymmetric showing only either bright or dark contrast. In these cases, the application of an external voltage bias to the grain boundary of several ten’s of millivolts is necessary to restore a symmetrical barrier structure. The orientations of grains on either side of each grain boundary were determined using electron backscattered pattern (EBSP) analysis and the grain boundary plane orientation was calculated by observing the lateral shift of the grain boundary EBIC contrast peak with SEM beam voltage and, hence, penetration depth. It was found that the electrical asymmetry is governed by the orientations of the grain boundary planes on either side of the interface, demonstrating some crystallographic control of the barrier structure.




31.    Leach, C. (2005). "Grain boundary structures in zinc oxide varistors." Acta Materialia 53(2): 237-245.

Lattice misorientations across electrically active interfaces in antimony and bismuth doped zinc oxide varistors have been determined by electron backscattered pattern analysis and coupled with the orientations of the associated grain boundary planes established by depth resolved electron beam induced current (EBIC) in order to index the crystal faces forming either side of the grain boundary plane. When correlated with the EBIC contrast observed at the grain boundary, it was found that a symmetrical EBIC profile was only found at interfaces where both crystal faces forming the grain boundary were oriented at a similar angle from the polar basal plane orientation. At the majority of grain boundaries the structure was such that one face lay close to the basal plane orientation with the other face much further away. In these cases the EBIC was suppressed on the side of the grain boundary whose face lay close to the basal orientation. The implications of these observations on the electrical structure of the interface and microstructural development are discussed.




32.    Lebensohn, R. A., O. Castelnau, et al. (2005). "Study of the antiplane deformation of linear 2-D polycrystals with different microstructures." International Journal of Solids and Structures 42(20): 5441-5459.

The effective behavior and the distribution of local mechanical fields of linearly viscous 2-D polycrystals under antiplane shear is investigated. Several microstructures are considered, and a full-field approach based on the Fast Fourier Transform technique is applied. First, the accuracy of this technique is evaluated on a strictly isotropic 2-phase microstructure. Voronoi tessellation is then used to generate artificial microstructures, and a real (fully recrystallized) polycrystalline microstructure is obtained by electron back-scattering diffraction. Ensemble averages over several configurations using eight crystalline orientations (phases) are performed. Although a slight anisotropy is obtained for the effective behavior of each individual configuration, statistically, the results are in very good agreement with the available analytical isotropic solution. At phase level, a marked asymmetry is obtained for the distribution of local stresses. The intraphase first- and second-order moments of the stress field, calculated for both microstructures are compared with corresponding self-consistent predictions.




33.    Lee, C. S., F. C. Ng, et al. (1998). "The effect of rolling geometry on the distribution of deformed cube structure and its recrystallisation kinetics." Materials Science and Engineering A257(1): 198-203.

The microstructure, distribution and recrystallisation kinetics of cube-oriented deformation structures in copper cold rolled at two different rolling geometries were studied. It was found that a suitable amount of redundant shear strain during rolling increases the density and volume fraction of the cube-oriented deformation structure. In addition, the cube-oriented structure at the rolling sheet surface, where the redundant shear strain is generally larger than that at the centre region, was found to have a smaller average misorientation angle from the exact cube orientation. Irrespective to these factors, the cube-oriented structure formed by rolling at a high redundant shear condition recrystallises much slower than that formed at a lower redundant shear condition. On the other hand, this observation is consistent with the fact that the 25–40° <111>misorientation relationship between the cube-oriented structures and their neighbours is least frequently found in the regions of large redundant shear. That is, many of the cube-oriented structures formed with a high redundant shear do not have neighbours with the favourable 25–40° <111> misorientation relationship for high rate of grain boundary migration during recrystallisation. © 1998 Elsevier Science S.A. All rights reserved.




34.    Lee, D. N. and H. J. Lee (2004). Self-Annealing Textures of Copper Damascene Interconnects. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.




35.    Lee, D. N. and H. Park (2003). "The evolution of annealing textures in 90 Pct drawn copper wire." Metallurgical and Materials Transactions A 34A(3): 531-541.

An electrolytic copper rod was drawn in 24 passes to a 90 pct reduction in area and subsequently annealed under various conditions. The global texture of the drawn wire, as measured by X-ray methods, showed a fiber texture approximated by a strong <111> and a weak <100> component. However, its microtexture, as measured by electron backscattered diffraction (EBSD), indicated that the major <111> + minor <100> duplex fiber texture was dominant only in the center region, while a relatively diffuse texture developed with a somewhat higher density of orientations having a <11w>//wire axis in the middle and surface regions. The inhomogeneous texture in the as-deformed wire gave rise to an inhomogeneous microstructure and texture after annealing. When annealed at 300 degrees C or 600 degrees C for 3 hours, the wire developed a duplex fiber texture consisting of major <100> + minor <111> components in the center region, a strong <100> fiber texture in the middle region, and a weak texture consisting of <111> and <100> components with the <111> component being slightly stronger in the surface region. When the drawn wire was annealed at the high temperature of 700 respecti C, the texture at short annealing times was similar to that of the wire annealed at the lower temperatures of 300 degrees C and 600 degrees C for 3 hours, but prolonged annealing gave rise to a texture ranging from the <111> to <112> components due to abnormal grain-growth that started in the surface region. The recrystallization texture consisting of the major <100> + minor <111> components was explained by the strain-energy-release maximization (SERM) model, in which the recrystallization texture is determined such that the absolute maximum principal stress direction due to dislocations in the deformed state is along the minimum elastic-modulus direction in recrystallized grains. On the other hand, the abnormal grain-growth texture was attributed to grain-boundary mobility differences between differently oriented grain.




36.    Lee, D. N. and H.-C. Lee (2003). "Effect of Stresses on the Evolution of Annealing Textures in Cu and Al Inteconnects." Journal of Electronic Materials 32(10): 1012-1022.

A new model is advanced to account for the evolution of annealing textures in copper and aluminum interconnects based on strain and surface energies. The interconnects, whether they are conventionally or damascene-process fabricated, are subjected to stresses during room temperature or elevated temperature annealing, which in turn, gives rise to strain energies. The strain energy of a deposit is influenced by its texture and geometry. The annealing texture of an interconnect line is determined such that its elastic strain and surface energies are minimal. The measured textures in damascene-processed copper interconnects and a published result of conventionally processed Al-1%Cu interconnects are discussed based on minimization of their strain and surface energies.




37.    Lee, D. N. and J. K. Lee (2004). Shear texture development and grain refinement in asymmetrically rolled aluminum alloy sheets: Effects of shear combinations. Ultrafine Grained Materials III (as held at the 2003 TMS Annual Meeting), Charlotte, North Carolina, USA.

Asymmetric rolling, in which the ratio of the rotation rates of the upper and lower rolls was 2, has been used to introduce an intense plastic shear strain for the purpose of grain refinement and developing shear deformation textures through the sheet thickness to improve the strength and plastic strain ratio of AA1050 aluminum alloy sheets. The alloy sheets were rolled at room temperature without lubrication. The textures and microstructures of the sheets were investigated by x-ray diffraction and electron back-scattered diffraction (EBSD) analyses with emphasis on effects of combinations of rolling directions.




38.    Lee, H.-J., D. I. Kim, et al. (2005). "Electron backscattered diffraction analysis of copper damascene interconnect for ultralarge--scale integration." Thin Solid Films 474(1-2): 250-254.

This study focuses on the structures and the crystallographic orientations of copper electrodeposits in trench patterns by the electron backscattered diffraction (EBSD) technique. The EBSD measurement was made on the surface of annealed deposits before and after removal of their over--plated layers by chemical mechanical polishing (CMP) and also on the section normal to trench lines. The textures of the annealed deposit with and without the over--plated layer are almost same. The major and minor orientation components in the annealing textures of trench specimens were approximated by {111}<110> and its twin components, {115}<110> and {115}<141>, respectively. Here {hkl}<uvw> indicates that {hkl} is the crystallographic planes parallel to the trench base plane and <uvw> is the crystallographic directions parallel to the trench line direction. By measuring the line--normal sectional EBSD analysis, the copper electrodeposit in a trench plug is figured as a single crystal having a few of twinning, and hence the over--plated layer has almost the same texture as the trench plug. Therefore, the texture of trench plugs can be inferred by that of the over--plated layer.




39.    Lee, H.-J., K. H. Oh, et al. (2004). Cross-sectional crystallographic analysis of copper electrodeposits for ULSI metallkation by EBSD. 205th ECS Meeting, San Antonio, TX, United States.

For cross-sectional EBSD(electron backscatter diffraction) analysis, FIB(focused ion beam) milling and coating of conducting materials(carbon or gold) are developed to smooth the rough cutting surface and decrease the charging effect caused by IMD(inter-metallic dielectric) deposits. The copper electrodeposits in trench plug are figured as a single crystal having a few of twinnings. Interestingly, the crystallographic orientation of the overplating region is also founded to be same as that of trench plug. Additionally this experiment shows that the texture of overplating region also as the [111]<110> texture, as same as the texture in trench plug. Namely the recrystallization, which has initiated at the specific point in trench plug, can be propagated into the overplating region. Conversely, the movement of grain growth in a trench plug during self-annealing can be inferred by measuring that in the overplating region. Therefore, the in-situ planar EBSD analysis for a self-annealed specimen shows that the grain growth is initiated at the pattern area and the grain usually grows isotropically.




40.    Lee, J. G., A. U. Telang, et al. (2002). "Modeling Thermomechanical Fatigue Behavior of Sn-Ag Solder Joints." Journal of Electronic Materials 31(11): 1152-1159.

Stresses that develop because of the coefficient of thermal expansion (CTE) mismatch between solder and substrate/components contribute to thermomechanical fatigue (TMF) of the solder joints. However, the relative importance of several processes that contribute to damage accumulation and its role in affecting the reliability of the solder joints are far from being understood. Aging, creep/stress relaxation, and stress/strain reversals are some of the important processes. These processes are affected by service conditions, such as the temperature extremes as experienced, rates of heating and cooling, dwell times at the extreme temperatures, and so on. In addition, the elastic and plastic anisotropy of tin could also contribute to the damage accumulation during TMF in Sn-based solders. This preliminary effort to model TMF in Sn-Ag solder joints will consider the role of each of these parameters, with significant emphasis on the anisotropic-elastic behavior of Sn grains.




41.    Lee, J. K. and D. N. Lee (2002). Shear Texture Development and Grain Refinement in Asymmetrically Rolled Aluminum Alloy Sheets by Varied Reduction per Pass. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.

Asymmetric rolling, in which the ratio of the upper to lower roll diameter was 2, has been used to introduce an intense plastic shear strain for the purpose of grain refinement and developing shear deformation textures through the sheet thickness to give rise to higher plastic strain ratios and strengths of aluminum alloy sheets. AA1050 sheets were asymmetrically cold rolled without lubrication, and the textures and microstructures of the sheets were investigated by X-ray diffraction and electron back-scatter diffraction (EBSD) analyses. When subjected to several passes of asymmetric rolling, the sheets exhibited the textures approaching the ideal shear textures, {001}<110>, {111}<110>, and {111}<112> through the thickness and comprised fine-grained microstructures with high boundary misorientations. Finer grain microstructures were obtained at rolling reductions per pass of 5 and 50% than at 10, 20, and30%. The results were correlated to the l/d parameter, where l and d are the projected contact length and the mean sheet thickness in the deformation zone.




42.    Lee, J.-C., J.-Y. Suh, et al. (2003). "Work-softening behavior of the ultrafine-grained Al alloy processed by high-strain-rate, dissimilar-channel angular pressing." Metallurgical and Materials Transactions A 34(3): 625-632A.

Commercially pure Al alloy sheets were processed using high-strain-rate, dissimilar-channel angular pressing (DCAP) for as many as 100 passages through a channel with phi = 120 deg, to investigate the work hardening caused by a low strain level (epsilon < 2) and the work softening caused by an extremely high strain level (3 < epsilon < 58). The hardness of the alloy increased significantly by a factor of 2 at strains less than approx =2, while a gradual decrease in the hardness was observed at strains greater then approx =2. The work-hardening and the work-softening behaviors observed from the Al alloy were analyzed by correlating the measured properties with microstructural evolutions observed by transmission electron microscopy (TEM). A detailed microstructural-evolution sequence occurring at successive strain stages was also investigated based on TEM and electron backscattered diffraction (EBSD). Material: 1050 aluminum alloy.




43.    Lee, K., A. C. C. Reis, et al. (2005). "Evaluation of stored energy after accumulative roll bonding of an interstitial-free steel by means of orientation microscopy data." Journal of Applied Crystallography 38: 668-674.

The stored energy of warm-rolled interstitial-free steels, produced in an accumulative roll bonding process, is evaluated by using the textural and microstructural information contained in orientation imaging microscopy (OIM) scans which were measured after accumulated von Mises strains (εvM) of 0.8, 1.6, 2.4 and 4.0, respectively. It is assumed that the plastic strain energy is stored in a cellular network of local boundaries of low and high misorientations. The presence of intracellular dislocations which do not contribute to a local crystal orientation gradient is ignored in the present analysis. On the basis of the Read–Shockley equation, the local misorientation can be associated with a local boundary energy which can be expressed as a local stored energy by taking into account the radius of curvature of the cellular network. The validity of this procedure was verified by comparing the integrated average stored energy of the sample with the Vickers hardness data, which produced a reasonable correspondence. The present analysis also allowed the calculation of the stored energy distribution in the areas of the orientation representation space which were sufficiently populated by sample crystal orientations, i.e. the γ fibre (<111>||ND) of the present deformation texture. The distribution of stored energy along this fibre displayed a maximum on the {111} <211> texture component, particularly after a von Mises strain of 1.6, whereas the {111}<110> component displayed a local minimum of stored energy after εvM = 2.4 and 4.0.




44.    Lee, K., G. Kim, et al. (2005). Effect of Initial Texzture on the Evolution of Texture and Stored Energy During Recrystallization of Interstitial Free Steel. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.

By applying a double cold rolling and annealing treatment, the evolution of the α and γ fiber components differed from the ones observed in conventional processing. This is attributed to the difference of the initial texture. An increased reduction of stored energy of the {111}<112> component was found by monitoring the change of the stored energy during annealing, indicating that the onset of the nucleation stage of recrystallization by relaxation and annihilation of dislocations occurred mainly on the {111}<112> component with its higher stored energy. The detailed texture evolution of the double cold rolled specimen during 2nd annealing is described by coupling the theory of oriented nucleation and orientation pinning, which is experimentally confirmed by OIM scan.




45.    Lee, K.-H., Z. Jiang, et al. (2002). "A scanning electron microscope study of the effects of dynamic recrystallization on lattice preferred orientation in olivine." Tectonophysics 351: 331-341.

Effects of dynamic recrystallization on lattice preferred orientation (LPO) in olivine were investigated through the combination of two SEM-based techniques, electron backscattered diffraction (EBSD) technique for crystallographic orientation measurement and backscattered electron imaging (BEI) for dislocation observation. Samples are experimentally deformed olivine aggregates in simple shear geometry. In the sample deformed at T = 1473 K and high stresses (f480 MPa), only incipient dynamic recrystallization is observed along grain-boundaries. Orientations of these small recrystallized grains are more random than that of relict grains, suggesting an important role of grain-boundary sliding at this stage of recrystallization. In the sample deformed at T = 1573 K and low stress (f160 MPa), dynamic recrystallization is nearly complete and the LPO is characterized by two [100] peaks. One peak is located at the orientation subparallel to the shear direction and is dominated by grains with high Schmid factor. The other occurs at high angles to the shear direction and is due to the contribution from grains with low Schmid factor. Grains with high Schmid factor tend to have higher dislocation densities than those with low Schmid factor. Based on these observations, we identify two mechanisms by which dynamic recrystallization affects LPO: (1) enhancement of grain-boundary sliding due to grain-size reduction, leading to the modification of LPO caused by the relaxation of constraint for deformation; (2) grain-boundary migration by which grains with lower dislocation densities grow at the expense of grains with higher dislocation densities. Based on the deformation mechanism maps and stress versus recrystallized grain-size relation, we suggest that the first mechanism always plays an important role whereas the second mechanism has an important effect only under limited conditions.




46.    Lee, P. S., A. D. Rollett, et al. (1999). Development and application of a disorientation correlation function. Twelfth International Conference on Textures of Materials (ICOTOM 12), McGill University, Montreal, Canada, NRC Research Press.




47.    Lee, P. S., H. R. Piehler, et al. (1998). "Influence of surface texture on orange peel in aluminum." Journal of Materials Processing Technology 80-81: 315-319.

To investigate the surface finish and roughening behavior of aluminum alloys, we combine the automated analysis of electron back scattered patterns (EBSP) with surface topography data obtained from an interference microscope. A 6022 commercial aluminum alloy, which is used for automobile body panels, was studied in the T4 condition. The sheet tensile samples were designed to be close to plane strain deformation. Various techniques to generate maps and correlation function are used to show quantitative results of the correlation. The texture of the aluminum sheets combined rolling and annealing components, with the strongest component being the cube component ({100}<001>). No clear relationship was identified between orange peel development and the crystallographic orientation of the surface grains.




48.    Lee, P. S., H. R. Piehler, et al. (2002). "Texture Clustering and Long-Range Disorientation Representation Methods: Application to 6022 Aluminum Sheet." Metallurgical and Materials Transactions A 33A(No. 12): 3709-3718.

Two new graphical methods are presented for microstructural analysis of crystalline material. These analyses are intended to aid an understanding of deformation behavior at scales larger than the grain size. The correlation of orientation over long distances has rarely been investigated, since a long-range correlation has been assumed to be negligible, if present at all. The first method reveals orientation clustering by calculating the variance of the orientation distribution function (ODF). The second addresses orientation ordering or orientation autocorrelation and is named the disorientation correlation function (DCF). We show that both analyses can be derived from the two-point autocorrelation functions of the orientation field.




49.    Lee, S. Y., Y. B. Chun, et al. (2003). "Effect of thermomechanical processing on grain boundary characteristics in two-phase brass." Materials Science and Engineering A 363(1-2): 307-315.

Commercial 60Cu-40Zn two-phase alpha - beta ' alloy was thermomechanically processed to enhance the special low CSL boundaries. Repeated cycles of cold rolling (20%) and heat treatment (680 deg C/20 min) resulted in an increase in Sigma 3 boundaries in the alpha phase that were identified as the annealing twins in the Electron Backscattered Diffraction analysis. The identical processing, however, produced a high frequency of low angle boundaries within the beta ' phase. Formation of annealing twins in the alpha phase was accompanied by randomization of the texture of the starting material. The present result demonstrates the effectiveness of this thermomechanical processing in promoting annealing twins in the fcc alpha phase compared to the bcc beta ' phase of commercial brass.




50.    Lee, S.-L. and N. L. Richards (2005). "The effect of single-step low strain and annealing of nickel on grain boundary character." Materials Science and Engineering A 390: 81-87.

Combinations of a lowtensile strain and annealing temperature have been successfully processed to double the fraction of special boundaries, Σsp, in commercially pure (C.P.) nickel. Processing sequence of one step of 6% strain followed by a 900 °C anneal for 10 min, has resulted a special boundary fraction (3 ≤ Σ ≤ 29) of 74.7%, compared to the as-received material of 36.5%. A large proportion of this increased in special boundaries were found to be made up of annealing twins Σ3 and its twin variants Σ3n. Deformation applied to the sample alone without heat treatment, caused the fraction of special boundaries, to decrease, the Σsp value falling, for example to 25.6% at 12% strain. Energy minimization processes such as grain boundary migration and grain growth were suggested as means of enhancing the formation of annealing twins.




51.    Lee, S.-L. and N. L. Richards (2005). "Influence of long term annealing on grain boundary character distributions in nickel." Materials Science and Engineering A 405(1-2): 74-85.

Experiments were designed to study the long term annealing behaviour of commercially pure nickel. Low strain levels and moderate annealing temperatures of 700 and 800°C were utilized for times up to 168 h and evaluated for special boundary percentages using electron back-scattered diffraction. The effect of extended annealing times at both temperatures was to increase substantially the percentage of special boundaries over the range, S(3-29), including the twin related Σ3n types. The increase in the percentage of special boundaries was interpreted in terms of dislocation generation at grain boundaries during straining and the annealing out of these extrinsic grain boundary dislocations by climb along the grain boundaries and movement of the boundaries during the annealing process.




52.    Lee, T. C., I. M. Robertson, et al. (1989). "An HVEM Insitu Deformation Study of Nickel Doped with Sulfur." Acta Metallurgica 37(2): 407-415.




53.    Lee, T. C., I. M. Robertson, et al. (1990). "TEM Insitu Deformation Study of the Interaction of Lattice Dislocations with Grain-Boundaries in Metals." Philosophical Magazine A 62(1): 131-153.




54.    Lee, W. B., J. Furley, et al. (1992). "Misorientation texture of post-recrystallized alpha-brass." Journal of Materials Science 27(12): 3395-3399.




55.    Lefebvre, F. Micromechanical assessment of fatigue in airframe fusion welds, University of Southampton (United Kingdom). Ph.D.: 439.

The present study concentrates on micro-mechanical aspects of fatigue performance in a fusion welded airframe alloy, 2024-T351. Within the overall program the initiation and growth of short fatigue cracks was studied for two forms of welding: Metal Inert Gas (MIG) and Variable Polarity Plasma Arc (VPPA). Fatigue testing has been carried out on relatively small samples in 3-point bending at constant amplitude and at a R-ratio equal to 0.1. During the tests, replication techniques were used to determine crack initiation points and crack length as a function of the number of fatigue cycles. Secondary electron and back-scattered imaging observations, in association with electron back-scattered diffraction mapping, were carried out on failed samples to determine the crack initiation sites and assess the associated microstructural interactions. Optical microscopy, differential scanning calorimetry and transmission electron microscopy studies have also been carried out to elucidate the local inicrostructural conditions of the different elements of the welds. Thereby a balance between aging, overaging, re-solutionising and re-precipitation has been identified across the heat affected zone.It is concluded that several fatigue crack initiation processes may occur within the welds, each with its own implications for performance/lifing. Fatigue life of the MIG welds is controlled in the fusion zone by the combined effects of interdendritic defect sizes, crack coalescence, and, to a lesser degree, residual stresses. In the VPPA case, the fusion zone presents a much finer, lower density of crack initiating defects, and although crack initiation is indeed clearly seen in the fusion zone, fatigue life then becomes limited by the high peak residual stress levels of the VPPA heat-affected zone (HAZ) and the 'naturally occurring' defect population of the parent material. In the context of multiple crack interactions, an engineering micromechanical modelling has been successfully developed to predict the fatigue life of the MIG fusion zone and autogeneous VPPA HAZ (1mm crack length) as a function of the probability of initiation and the density/distribution of pores (or intermetallic particles). Semi-empirical crack growth rate approximation and a rnicrostructural crack growth rate approach are used. First order estimates of short crack closure behaviour are used to introduce a residual stress influence on crack growth rates model.




56.    Lefebvre, F. and I. Sinclair (2005). "Micromechanical aspects of fatigue in a MIG welded aluminium airframe alloy Part 2. Short fatigue crack behaviour." Materials Science and Engineering A 407(1-2): 265-272.

Short crack fatigue behaviour of a metal inert gas (MIG) welded 2024-T351 aluminium alloy has been studied in terms of crack initiation and propagation, and the microstructural features of the weld. Extensive crack initiation was noted within the weld fusion zone. Relatively small interdentritic defects are seen to be more damaging (in initiating cracks) than the larger gas bubble defects that exist in this region. Cracks were also seen to initiate within the weld heat affected zone where tensile residual stresses were found to be high, however, rapid crack growth and coalescence within the fusion zone is seen to dominate failure. Multiple crack interactions are seen to have a significant effect on failure up to relatively large crack lengths (of the order of the fusion zone width), enhancing the variability in short crack growth. Secondary electron and back-scattered electron imaging, in association with electron back-scattered diffraction (EBSD) mapping, were carried out on failed samples to assess the associated microstructural interactions.




57.    Lefebvre, F., S. Ganguly, et al. (2005). "Micromechanical aspects of fatigue in a MIG welded aluminium airframe alloy. Part 1. Microstructural characterization." Materials Science and Engineering A 397(1-2): 338-345.

Fusion welding of high strength aluminium alloys is being widely considered within the commercial aircraft industry as an alternative to established mechanical fastening methods. The objective of the present article is to characterise the microstructural features of metal inert gas (MIG) welded plate of the conventional damage tolerant alloy, 2024-T351. Micromechanical aspects of the fatigue performance of this welded material are then addressed in a companion article. The general microstructure of the MIG weld was studied using optical microscopy and scanning electron microscopy, in association with electron back-scattered diffraction mapping. Columnar dendritic structures at the edge of the fusion zone are seen, with fairly uniform equiaxed dendritic grain structure dominating in the weld centre. Local microstructural conditions of the different elements of the weld have been assessed via micro-hardness and differential scanning calorimetry, identifying the balance between aging, overaging, re-solutionising and re-precipitation occurring across the weld region. Residual stress measurements by laboratory X-ray and synchrotron X-ray diffraction are also discussed, showing stress relaxation and redistribution occurring under loads representative of smooth specimen fatigue testing. The fusion zone is seen to present a tensile residual stress field, with peak longitudinal stress occurring towards the interface with the fusion zone.




58.    Lehockey, E. M., A. M. Brennenstuhl, et al. (2004).  "On the relationship between grain boundary connectivity, coincident site lattice boundaries, and intergranular stress corrosion cracking." Corrosion Science 46(10): 2383-2404.

The present work reports on refinements proposed to existing models for predicting the distribution of intergranular stress corrosion cracking based on the frequency of "special", crack-resistant, low-Σ CSL grain boundaries in the microstructure. The accuracy of these models in predicting the extent of intergranular cracking in low-stacking fault FCC materials ranging from Alloy 600 to Admiralty Brass is improved by factors ranging from 2 to more than 6 by discounting isolated, "neutral-twins" from the measured total special boundary fraction. A stochastic model is presented for easily and accurately determining the proportion of neutral-twins, which do not disrupt connectivity in the network of random boundaries based on the relative frequency of twin-variant boundaries (i.e. Σ9s and Σ27s) in the microstructure. Improvements in the predicted susceptibility to intergranular attack achieved from the refinements described herein will enhance current abilities to identify components at high risk of failure by IGSCC based on grain boundary structure.




59.    Lehockey, E. M., G. Palumbo, et al. (1996). On the relationship between grain-boundary character distribution and intergranular corrosion. Microscopy and Microanalysis 1996. G. W. Bailey, J. M. Corbett, R. V. W. Dimlich, J. R. Michael and M. J. Zaluzec. San Francisco, San Francisco Press: 346-347.




60.    Lehockey, E. M., G. Palumbo, et al. (1998). Effect of Grain Boundary Structure in Reducing Susceptiblity of Lead-Acid Battery Grids to Corrosion, Creep and Cracking. Boundaries and Interfaces in Materials: The David A. Smith Symposium. R. C. Pond, W. A. T. Clark and A. H. King. Warrendale, Pennsylvania, The Minerals, Metals and Materials Society: 45-50.




61.    Lehockey, E. M., Y.-P. Lin, et al. (2000). Mapping Residual Plastic Strain in Materials Using Electron Backscatter Diffraction. Electron Backscatter Diffraction in Materials Science. A. J. Schwartz, M. Kumar and B. L. Adams. New York, Kluwer Academic/Plenum Publishers: 247-264.




62.    Lei, T. S. and D. S. Yang (2004). "Characterization of carbide growth in directionally solidified high chromium white cast iron." JOM 56(11): 184.

The characterization of carbide growth in directionally solidified castings of ASTM A532-87 Class V high chromium white cast iron is investigated. A vertical cylindrical casting set-up which consists of two layers of Furan sand mold and sandwiched with a chilled copper mold was used for directional solidification. This solidification set-up provides three zones with different solidification direction: an upward zone above the chilled mold, a bidirectional solidification zone within the chilled copper mold, and a downward zone below the chilled mold. Due to the effect of gravity and fluid convection the solidification characteristics in these three zone are different. The morphology of primary alloy carbide M7C3 shows differences in these three zones, specifically, long rods of M7C3 carbide up to 3 mm were grown in the chilled mold. Other than SEM used for morphologies, the EBSD results will be used to study the preferred crystallographic orientation of the M7C3.




63.    Lei, T. S., W. S. Chang, et al. (2006). "The effect of fluid convection on microstructures of directionally solidified castings." Materials Science Forum 508: 473-478.

Fluid convection during solidification of castings will influence the final structures of the castings. A vertical cylindrical casting set-up has been designed to provide two zones of solidification simultaneously with two moving fronts directionally upward and directionally downward, respectively. This two zone directional solidification casting was composed of a cylindrical Furan sand mold with a water chilled center hole block at the center of the casting. Experimentally it was observed that the cooling rates at different locations of the downward zone were much more even than those of the upward one and this is considered to be the result of a more even temperature distribution along the downward front moving zone due to stronger fluid convection. Fluid convection tends to mix up the liquid and results in a more even temperature distribution and a lower degree of segregation of the element molybdenum which has a strong tendency to segregate to the carbide in ductile iron. The characteristics of the matrix microstructure and the growing direction of carbide of this directionally solidified ductile iron has been investigated with SEM and EBSD techniques.




64.    Leinum, J. R., K. Moen, et al. (2004). EBSD – a supplementary technique in automatic characterisation of geological samples with chemically similar minerals. European Microscopy Congress 2004, Antwerp, Belgium.

Application of automatic characterisation of mineral raw materials and beneficiated products is of major importance in mineral processing. Some established methods for quantitative analysis of minerals are optical methods, SEM-based methods, X-ray methods (XRD, EDS/WDS) etc. Especially SEM-based techniques have gained wide use, and i.e. Lastra et al. (1998) [1] describe a system based on a complex image analysis program which by means of grey-level ranges and different X-ray count rates, copes with very complex chemistry in modal analysis. In industrial minerals raw material the occurrence of the same elements in different minerals is common. Sometimes the various minerals not only contain the same elements, but also about the same amount of elements. In these cases chemical analyses are not sufficient to identify the minerals. As a supplementary technique in these cases, application of crystallographic information by electron backscatter diffraction [2] (EBSD) is very suitable. The technique is until now not frequently utilised on geological samples, but will find a wide application together with the low vacuum SEM. The technique has been demonstrated on raw material from A/S Olivin in Norway. The material contains forsterite (Mg1,86Fe0,14SiO4) and enstatite (Mg0,94Fe0,06SiO3) which are very similar chemically. Enstatite is unwanted in the concentrate, so quantitative description of the mineral is important. The specimens were prepared into polished thin sections which were ion beam etched (5kV, 5mA, 3h) to get a surface with as little deformation as possible and then moderately carbon coated to get rid of some charging effects. EBSD investigations were carried out in a JEOL 840 scanning electron microscope (SEM) equipped with NORDIF EBSD hardware and HKL Channel 5 EBSD software to produce EBSD grain and phase maps. The SEM operated at 30kV to penetrate through the carbon layer using a tilt angle of 70°, a working distance of 23 mm and a probe current of 1-6nA. Misindexing due to microfractures in the phases and the disturbing carbon layer was a bigger problem than low indexing fraction. Applying 6 strong bands for indexing the diffraction patterns yielded the most optimum map. Finally, a Kontron image analysis system was used to “close” misindexed areas and make a binary image for quantification of the minerals. The demonstration shows that EBSD is able to discriminate the two minerals, which is impossible by means of all other automatic methods. The charging problems that we encounter in the traditional SEM will be overcome in a low vacuum SEM without carbon coating the specimen. This will in turn lead to a better diffraction pattern and better indexing. EBSD may be linked with the techniques described by Lastra et al. (1998) [1] and is superior as an automatic technique in characterising various modifications of phases as well as in characterisation of minerals in grinding products where the grain size is too small for individual analysis of the particles using chemical/optical techniques.




65.    Leiss, B. and D. J. Barber (1999). "Mechanisms of dynamic recrystallization in naturally deformed dolomite inferred from EBSP analyses." Tectonophysics 303(1-4): 51-69.

In order to investigate the mechanisms of dynamic recrystallization in dolomite, single grain orientation measurements on a mantled porphyroclast have been carried out by means of electron back-scattered patterns (EBSPs). The local orientations in the grain fabric were analysed to establish meaningful orientation families. In addition to a twinned grain, the porphyroclast consists of two domains, each with a specific orientation pattern. Both domains are polygonized by subgrain rotation, which gives great- and small-circle dispersion patterns of the crystal orientation data in the pole figures. However, even the simple and well-defined dispersion patterns for which one can assume a single slip system are not consistent with any of the theoretical dispersion patterns of the known slip systems. Additional mechanisms like rigid body rotation, nucleation and/or combinations of different slip systems are the likely explanation. No definitive orientation relationship has been found between the porphyroclast and the mantle. The lack of such a relationship, together with the shape of the grain boundary, point to grain boundary migration. The texture of the mantle agrees with the global texture of the sample, indicating that mechanisms of crystal plasticity were active during flow around the clast. The results demonstrate the potential of EBSP data for the deduction of active mechanisms, but a proper interpretation requires a better theoretical foundation. This could be achieved by modelling dispersion patterns for different mechanisms and different combinations, and by including orientation correlations.




66.    Leiss, B., K. Ullemeyer, et al. (2000). "Recent Developments and Goals in Texture Research of Geological-Materials - Preface." Journal of Structural Geology 22(11-12): 1531-1540.




67.    Lenain, A., N. Clément, et al. (2005). "Characterization of the α Phase Nucleation in a Two-Phase Metastable β Titanium Alloy." Journal of Materials Engineering and Performance 14(6): 722-727.

Beta titanium alloys are increasingly the best choice for automotive and aerospace applications due to their high performance-to-density ratio. Among these alloys, the TIMETAL Ti-LCB is already used in the automotive industry because it presents excellent mechanical properties and a lower cost compared with other Ti alloys. The current study deals with the characterization of the nucleation and growth of the α phase in several thermomechanical processes, because the distribution and size of the α phase strongly influence the mechanical properties of the resulting microstructures. Several heat treatments were conducted after either cold rolling or annealing. The resulting microstructures were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, or electron backscatter diffraction. It was observed that the morphology and the volume fraction of the α phase are strongly dependent on the holding temperature, on the heating or cooling rate, and on the β grain size.




68.    Lenarduzzi, E., E. L. Bounie, et al. (2003). "Titanium Oxidation During Thermal Treatment: Inhibiting Role of Nitrogen and Epitaxial Orientation Relations Evidenced by EBSD." Advanced Engineering Materials 5(8): 587-593.

There are numerous studies dealing with the oxidation of titanium and its alloys, in particular on TA6V during thermal treatment. It appears that these studies cannot be used so easily as they are as they are not reproducible. This observation can be attributed to an insufficient description of the procedure and/or different experimental conditions (the materials used are not identical or have not been produced under similar conditions, or the processing has been different, etc. As titanium has marked affinity to oxygen, the treatment is always carried out, either by replacing the atmosphere in the furnace by a neutral gas such as argon (as this gas always contain a more or less significant amount of oxygen) or under vacuum, be it primary or secondary vacuum (this process calls for heavy and expensive equipment). In all cases, out of precaution, oxygen getter are generally installed with a view to avoiding or restricting surface pollution. The purpose of this study relating to the thermal treatment of tubular parts for the aeronautics industry is to submit precise data (these are so-to-say non-existent for TAW) and an analysis of the phenomena involved during the oxidation of TA3V and T40 by making use of industrial atmospheres of the oxygen-nitrogen or oxygen-argon type and by varying the oxygen level (1 %, 10 %, 20 %) in a range of temperatures between 620 deg C and 850 deg C - these temperatures are used routinely for the thermal treatment of titanium.




69.    Lenhard, S., F. Wagner, et al. (1999). Texture, microstructure and properties in mechanically alloyed and extruded FeAl. Twelfth International Conference on Textures of Materials (ICOTOM 12), McGill University, Montreal, Canada, NRC Research Press.




70.    Lens, A., C. Maurice, et al. (2004). High Angle Grain Boundary Mobilities in a High Purity Single-Phase Al-0.1 wt% Mn Alloy. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.

The migration rates (V) of "random" high angle grain boundaries (HAGB) during annealing of a cold deformed (epsilon =1.3) high purity Al-0.lwt% Mn alloy were determined using a combination of in-situ annealing and EBSD in the SEM at temperatures between 200 and 330 deg C. The SEM heating stage used for these experiments is described and results on the local recrystallization kinetics of the Al-Mn alloy are presented. For this, the local stored energies (P) were determined by subgrain size and misorientation analyses to give the boundary mobilities (M) through the standard V = M.P equation. The solute drag "force" was analysed with the alomistic model of LUcke and Stuwe (1971) for a "loaded" boundary and used to estimate the diffusion rates in the above temperature range. The activation energies for boundary migration were found to be consistent with those of solute atoms moving behind the grain boundary, i.e. intermediate between the values for bulk and boundary diffusion of Mn.




71.    Lens, A., C. Maurice, et al. (2005). "Grain boundary mobilities during recrystallization of Al–Mn alloys as measured by in situ annealing experiments." Materials Science and Engineering A 403(1-2): 144-153.

The influence of Mn on the mobilities of grain boundaries during recrystallization of Al–0.1 and –0.3 wt.% Mn alloys has been characterized by in situ SEM annealing experiments. Polycrystals of high purity, single-phase Al–Mn alloys were deformed in channel-die plane strain compression at room temperature to strains of 1.3. The specimens were in situ annealed in an SEM/EBSD in order to measure grain boundary mobilities at temperatures between 200 and 450 °C. Stable “loaded” boundary migration was observed in the 0.1 and 0.3% Mn alloys. However, unstable, partially “free”, boundary migration could also be found in the 0.1% alloy. The mobilities, deduced from the migration rates and the stored energies, were consistent with the solute drag theories of Cahn, Lücke and Stüwe. The diffusion rates controlling the solute drag were of the same order for both theories and the activation energy for boundary migration was found to be intermediate between that of solute diffusion in the lattice and along the grain boundaries.




72.    Lenze, A., B. Stockhert, et al. (2005). "Grain scale deformation in ultra-high-pressure metamorphic rocks - An indicator of rapid phase transformation." Earth and Planetary Science Letters 229(3-4): 217-230.

Conspicuous grain scale deformation is observed in some ultra-high-pressure (UHP) metamorphic rocks of the Dora Maira Massif, Western Alps, although no significant strain is discernible on the mesoscopic scale. In a jadeite-kyanite-quartz rock, some of the jadeite crystals reveal (100) deformation twins, indicating local differential stress levels above 0.3 GPa. Many kyanite crystals show marked kink or deformation bands, with a slip system (100) 001. In contrast, the adjacent coarse-grained quartz matrix (grain size ca. 0.2 mm), which has formed from coesite during exhumation from >100 km depth, reveals a foam structure. The quartz grain boundary configuration is controlled by interfacial free energy, the grains are optically strain-free, and there is no crystallographic preferred orientation. Preservation of this foam microstructure, which indicates grain growth during low-stress annealing, precludes that deformation of the jadeite and kyanite crystals is a result of a late-stage low-temperature overprint. The orientation distribution of jadeite and kyanite with and without twins or deformation bands, respectively, has been investigated with a combination of universal stage and EBSD techniques. On the scale of a thin section, there is no preferred orientation of twinned jadeite and bent kyanite crystals and undeformed crystals, respectively. Thus, the orientation of the inferred local shortening direction is random. This precludes deformation driven by a homogeneous far field tectonic stress, but suggests an internally controlled stress field which is highly inhomogeneous on the scale of a few grain diameters. Laboratory experiments show that the coesite to quartz transformation proceeds within hours after decompression from 3.0 to 2.7 GPa at 800 degrees C. The microstructures of incompletely transformed samples indicate that the quartz growing at the expense of coesite undergoes crystal plastic deformation and recrystallizes with a very fine grain size during transformation. In this case, the deformation of quartz is attributed to the volumetric strain δV=+10% inherent in the coesite-quartz transformation, which causes a highly inhomogeneous stress field inside the sample related to the progress of the transformation. We propose that a similar process has taken place in the polyphase natural rock during exhumation, with the transient stresses causing mechanical twinning of jadeite and bending or kinking of kyanite. When the transformation had gone to completion, grain growth obliterated the microstructures of the quartz matrix, while the deformed jadeite and kyanite crystals preserved the record of inhomogeneous deformation at high temperatures. The peak differential stresses locally exceeded 0.3 GPa, which indicates very high strain rates and a correspondingly rapid transformation of coesite to quartz, comparable to the laboratory results. Copyright 2004 Elsevier B.V. All rights reserved.




73.    Lepper, M., A. von Glasow, et al. (1998). "Crystal texture and electromigration damage in Al-based interconnect lines studied by ACOM with the SEM." Materials Science Forum 273-275: 537-578.

Electromigration, as one of the main failure mechanismus of VLSI circuits, is of great concern to microelectronics industry. The effects of grain morphology as well as texture can be studied on a mesoscale by Automated Crystal Orientation Mapping (ACOM) in the SEM since it provides a detailed description of the microstructure. Textural functions (e.g. pole figures, ODF, MODF), statistical parameters (e.g. grains size distribution) as well as a graphical representation of grain structure (COM) can be extracted from the experimental aggregate function In `polycrystalline' (not yet `bamboo') structured Al-1%Si-0.5%Cu interconnects the spatial arrangement of grains in the line rather than texture seems to be the dominating effect for electromigration failure. (Author abstract) [References: 8]




74.    Levin, L., A. Tokar, et al. (2000). "Microstructural characterization of γTiAl base alloy by electron probe x-ray microanalysis and electron backscatter diffraction." Journal of Materials Science 35(15): 3923-3929.

Electron backscatter diffraction (EBSD) and electron probe x-ray microanalysis (EPMA) in combination with x-ray diffraction (XRD) were applied for phase identification of the ternary precipitates and accompanying phases in Ti-49.6Al-1.9Fe alloy after heat treatment at 1400°C followed by furnace cooling. The heat treatment resulted in formation of the duplex structure consisting of equiaxed grains of the γ phase (AuCu type) and lamellae of the g and α2 (Ni3Sn type). The ternary θ2 (Mn23Th6 type) phase, containing 21–22 at. % Fe, was revealed on the grain boundaries of the γ -matrix and lamellae, and is accompanied by α2 precipitates. Different morphologies of the t2 + α2 colonies were found to differ in chemical composition, coarse particles being depleted in titanium, and the fine particles enriched in it. The combination of EPMA and EBSD in scanning electron microscopy proved to be very effective in local phase identification of specimens with fine multiphase structure.




75.    Lewis, A. C., J. F. Bingert, et al. (2006). "Two- and three-dimensional microstructural characterization of a super-austenitic stainless steel." Materials Science and Engineering A 418(1-2): 11-18.

The microstructure of AL-6XN, a commercial super-austenitic stainless steel, was investigated using novel two- and three-dimensional (3D) analysis and characterization techniques. The austenite matrix, the second-phase σ precipitates, and the relationships between them have been analyzed, with particular emphasis on the true 3D microstructure of the material, including grain boundary character, grain morphologies and connectivity. A combination of serial sectioning with electron backscatter diffraction (EBSD) analysis allowed for reconstruction of individual grains, and definition of all five degrees of freedom of the grain boundary planes. Second-phase σ particle size and morphology, crystallography, composition, potential formation mechanisms, orientation relationships, and coherency with the matrix have been analyzed. These results provide boundary conditions for atomistic calculations of specific grain boundary structures as well as the basis for mesoscale image-based models of mechanical behavior of the microstructures.




76.    Li, B. L., A. Godfrey, et al. (2002). Investigation of Macroscopic Grain Sub-Division of an IF-Steel during Cold-Rolling. ICOTOM 13. D. N. Lee. Seoul, Korea, Trans Tech Publications Inc. Vols. 408-412: 1185-1190.

To investigate the process of grain scale sub-division, an isterstitial free (IF) steel, of initial grain size 120µm, was deformed by cold rolling to reductions of up to 50%. Grain sub-division was investigated both using back-scattered channelling contrast images, and from orientation measurements taken using the electron back scatter pattern (EBSP) technique. Initial examination of the EBSP data based on the variation along line scans in the rolling and normal directions (RD, ND) suggested that the deformation of the grains could be classified into a few characteristic patterns. A more detailed examination of the sub-division pattern was carried out by constructing maps of deviation to the grain mean orientation. This analysis shows that in many, but not all cases, large grain rotations are found in wide regions near grain boundaries and/or triple junctions. In only a limited number of grains, a pattern of macroscopic (deformation) banding may also be observed.




77.    Li, B. L., A. Godfrey, et al. (2004). "Microstructural evolution of IF-steel during cold rolling." Acta Materialia 52: 1069-1081.

The microstructural evolution during cold rolling of IF-steel up to reductions of 90% has been investigated using scanning and transmission electron microscope techniques. The deformation microstructures consist of similar features to those already identified in several FCC metals, namely cell blocks showing a pattern of subdivision on two levels. An important difference compared to FCC metals is an increased prevalence of strain localization, seen most directly by highly localized micro- shearing. An orientation dependence of the deformed microstructure is observed in that nearly all the extended dislocation boundaries and micro-shear traces are crystallographic, coincident either with {1 1 0} or {1 1 2} slip planes. A sharp fall in ductility seen between rolling reductions of 30% and 50% is attributed to the onset of localized micro- shearing. A flow stress calculation, based on linearly additive contributions from dislocation and grain boundary hardening, leads to flow stress values and a strain hardening behavior in good agreement with experimentally determined values.




78.    Li, C., P. Yang, et al. (2005). "Microstructures and microtextures of thermosonic-bonded gold in microelectronic packaging." Chinese Journal of Stereology and Image Analysis 10(4): 247-249.

The EBSD technique was used to investigate microstructures and microtextures of thermosonic bonded gold. It is shown that a dominant <111> and a weak <100> texture exist in cold drawn gold wires. During the first thermosonic bonding <100> oriented grains, which originate from the columnar grains in the free air ball, can be seen in the bond center region. Layer-formed grains caused by ultrasonic vibration are observed at the bonding interface. Recrystallization and abnormal growth are also found in overpowered bonds.




79.    Li, D. and C. J. Boehlert (2005). "Processing Effects on the Grain-Boundary Character Distribution of the Orthorhombic Phase in Ti-Al-Nb Alloys." Metallurgical and Materials Transactions A 36A(10): 2569-2584.

The grain-boundary character distribution of the orthorhombic (O) phase in Ti2AlNb intermetallic alloys was investigated. The alloys were thermomechanically processed either above or below the bcc transus temperature. Using electron backscattered diffraction, the twin-related O-phase variant interfacial planes were identified and quantified. For the subtransus-processed samples, the equiaxed-O/equiaxed-O grain boundaries tended to primarily prefer 65-deg misorientations and secondarily prefer 90-deg boundaries. Of the 65-deg misoriented boundaries, which were preferentially rotated about 001.40 pct contained (110) twin-related interfacial planes. The observations were rationalized by the α2-to-O phase transformation. It is suggested that for subtransus processing within the α2-containing phase regimes, the resulting heat-treated O + bcc microstructures evolve such that the O/O boundaries tend to exhibit distinct twin-related variants with misorientations between 55 and 65 deg. For a supertransus-processed alloy, it was found that approximately equal distributions of the six resolvable O variants were formed from the dominant parent bcc orientation. The resulting O/O boundaries tended to cluster at near-90-deg misorientations, which can be explained by the bcc/O orientation relationship. It is suggested that whenever the O phase primarily transforms from the bcc structure, the resulting O + bcc microstructures evolve such that the O/O boundaries tend to exhibit misorientations near 90 deg.




80.    Li, D., C. Liu, et al. (2005). "Characteristics of intermetallics and micromechanical properties during thermal ageing of Sn-Ag-Cu flip-chip solder interconnects." Materials Science and Engineering A 391(1-2): 95-103.

Sn–3.8 wt.% Ag–0.7 wt.% Cu solder was applied to Al–1 wt.% Cu bond pads with an electroless nickel (Ni–P) interlayer as an under bump metallisation (UBM). The microstructure and micromechanical properties were studied after ageing at 80 °C and 150 °C. Two types of intermetallic compounds (IMCs) were identified by electron back-scattered diffraction (EBSD), these being a (Cu, Ni)6Sn5 formed at the solder–UBM interface and Ag3Sn in the bulk solder. The (Cu, Ni)6Sn5 layer grew very slowly during the ageing process, with no Kirkendall voids found by scanning electron microscopy (SEM) after ageing at 80 °C. Nano-indentation was used to analyse the mechanical properties of different phases in the solder. Both (Cu, Ni)6Sn5 and Ag3Sn were harder and more brittle than the β-Sn matrix of the Sn–Ag–Cu alloy. The branch-like morphology of the Ag3Sn IMC, especially at the solder–UBM interface, could ultimately be detrimental to the mechanical integrity of the solder when assembled in flip-chip joints.




81.    Li, D., S. I. Wright, et al. (2004). "The grain boundary character distribution of a fully-orthorhombic Ti-25Al-24Nb(at.%) alloy." Scripta Materialia 51(6): 545-550.

The grain boundary character distribution (GBCD) of a fully- orthorhombic (O) Ti–25Al–24Nb (at.%) microstructure was investigated using electron backscatter diffraction (EBSD). The fine-grained (GS=17 µm) equiaxed microstructure was processed by hot forging and hot-rolling operations performed below the body-centered cubic (bcc) phase transus temperature followed by heat treatment in the O-phase field at 875 °C. Nearly all the O/O grain boundaries were greater than 15 degrees misoriented and such boundaries exhibited the highest frequencies at misorientations of approximately 65° (~26% of all grain boundaries) and 90° (~10% of all grain boundaries). Twin- related O-phase variant interfacial (110) planes were identified and such boundaries represented 39% of all the O/O grain boundaries with 65° misorientation about [001].




82.    Li, F., W. T. Roberts, et al. (1996). "Superplasticity and the Development of Dislocation-Structures in an Al-4.5-Percent Mg Alloy." Acta Materialia 44(1): 217-233.

The mechanical behaviour and development of microstructure in tension of an Al-4.5% Mg alloy at temperatures from 450 to 570°C and strain rates from 10-6 to 10-2 s-1 has been investigated. High strain rate sensitivities, up to m = 0.7, but relatively small elongations, between 120 and 280%, were observed. A single activation energy for deformation, close to reported values for self diffusion in aluminium, was obtained over the temperature and strain rate range used, and the strain rate and stress could be related using a hyperbolic sine function at constant strain. Tensile specimens were quenched and aged under stress to preserve the dislocation structures for examination by transmission electron microscopy. The dislocation structures observed showed a gradual and systematic change between regimes of power law creep at higher strain rates and diffusional creep at lower strain rates, and in the superplastic regime there was a tendency for small grains to be free of dislocations. Many of the dislocations had Burgers vectors inclined at about 45° to the stress axis, which suggests that they were active directly in response to the applied stress rather than as the result of a relaxation process accommodating grain boundary sliding.




83.    Li, H. and J. A. Szpunar (2005). "Software for simulation of diffusion process in polycrystalline material." Diffusion and Defect Data. Pt A Defect and Diffusion Forum 237-240(Part I): 219-223.

Understanding of diffusion processes in polycrystalline solids is of importance for studying processes like oxidation, precipitation, creep, superplastic forming, annealing and many other processes. In this paper, we will introduce our latest software that is able to simulate the diffusion process in poly and nano-crystalline solids. The diffusion process is simulated based on Random Walk theory. The diffusion matrix can be computer generated or obtained from the experimental measurement using Orientation Imaging Microscopy. The software describes microstructure and incorporates the effects of the material's texture, grain size and shape, grain boundary character distribution, statistical information on CSL boundary distributions, contribution from triple junctions and interfaces, the trapping of diffusing atoms and interaction of atoms with second phases and voids. A built-in database of diffusivities of various diffusing species and the user friendly interface make the software easy to use. The software is also applicable to thin films and multilayer structures. The output of simulation can be presented as a normalized concentration profile, a two-dimensional contour map of diffusing species, and also using many other statistical representations.




84.    Li, H., J. Park, et al. (2002). A Model of Recrystallization Process in Motor Lamination Silicon Steel. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.

A physically based computer model has been developed to simulate recrystallization process in Fe-Si motor lamination steel. The model assumes that each component of recrystallization texture nucleates at different stage of the process and has its own orientation. The deformed texture and microstructure, stored energy and the microstructure prior to deformation are among the major factors in determining the recrystallization texture. The experimental results show that the model is capable of predicting recrystallization texture.




85.    Li, J., S. L. Johns, et al. (2002). "The effect of hot zone velocity and temperature gradient on the directional recrystallization of polycrystalline nickel." Acta Materialia 50(18): 4491-4497.

Cold-rolled polycrystalline nickel sheets were directionally annealed at 1000°C with either a large (1000°C/cm) or a small (50°C/cm) temperature gradient ahead of the hot zone. Columnar grains were produced at hot zone velocities from 2 to 100 mm/h for the large temperature gradient with only two ~6 mm wide grains across the width at 5, 10 and 30 mm/h. With increasing hot zone velocity above 30 mm/h, the columnar grains became narrower. For the same range of hot zone velocities with a small temperature gradient, equiaxed grains were produced, with the grain size decreasing with increasing hot zone velocity. This difference arises because for the low temperature gradient recrystallization followed by substantial grain growth occurs ahead of the hot zone. Both interrupted directional annealing runs and runs (with the large temperature gradient) of nickel in which the nickel had been primary recrystallized at low temperature showed that the columnar grain structure developed by secondary recrystallization.




86.    Li, K., N. E. Ashbaugh, et al. (2004). Crystallographic initiation of nickel-base superalloy IN100 at RT and 538 degrees C under low cycle fatigue conditions. Superalloys 2004. Proceedings of the Tenth International Symposium on Superalloys sponsored by the TMS Seven Springs International Symposium Committee, in Cooperation with the TMS High Temperature Alloys Committee and ASM International, Champion, Pennsylvania, USA, TMS.

The crystallographic plane of IN100 at the initiation region of fracture surfaces under low cycle fatigue (LCF) conditions at RT and elevated temperature was identified. At RT fatigue cracks initiated on the {111} plane and at elevated temperature on the {001} plane. The initiation plane index was initially determined by investigating the gamma ' shape in the gamma matrix of fracture surfaces around crack initiation sites and finally verified by orientation image microscopy (OIM). An OIM scan on a sample of original material indicated that local texture might promote a fatigue crack to reach a critical crack size.




87.    Li, L., W. Yang, et al. (2003). "Dynamic recrystallization of ferrite during deformation at temperatures below ac(1) in a low carbon steel." Acta Metallurgica Sinica (China) 39(4): 419-425.

The hot deformation behavior of a Q235 class low carbon steel is investigated by plane strain compression tests on a Gleeble-2000 hot simulation test machine in the deformation temperature range of 700 to 550 deg C, i.e. ferrite phase range, with the strain rate range of 1x101 to 5x10-4 s-1, and the deformation microstructure evolution is investigated by means of SEM, TEM and EBSD The results indicate that under the present deformation conditions, dynamic recrystallization of ferrite, leading to grain refinement, is of continuous type at high hot deformation parameter Z values and discontinuous type at opposite conditions. The pearlites in this steel promote the progress of dynamic recrystallization. And the increase of parameter Z is of benefit to ferrite grain refinement that can lead to the formation of ultra-fine microstructures with average grain size of about 2 mu m.




88.    Li, L., W. Yang, et al. (2006). "Dynamic Recrystallization of Ferrite in a Low-Carbon Steel." Metallurgical and Materials Transactions A 37(3): 609-619.

Plane strain compression tests were performed on a low-carbon steel from 550 DGC to 700 DGC (ferrite-phase range) at strain rates of 10 to 5 X 10-4 s-1, and the deformation microstructure evolution was investigated by means of scanning electron microscopy, transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD). The results indicate that under the present deformation conditions, dynamic recrystallization of ferrite can occur in the low-carbon steel and lead to grain refinement. With increasing Zener-Hollomon parameter Z, the mechanism of this process changes from discontinuous dynamic recrystallization to continuous dynamic recrystallization; the turning point is approximately at Z = 1 X 1016 s-1. The increase of parameter Z leads to the decrease of recrystallized grain size of ferrite under steady state of deformation, and can lead to the formation of ultrafine microstructures with average grain size of about 2 mm.




89.    Li, M., K. Nagashio, et al. (2005). "Microtexture and macrotexture formation in the containerless solidification of undercooled Ni-18.7 at.% Sn eutectic melts." Acta Materialia 53(3): 731-741.

The microscopic orientations of Ni-18.7 at.% Sn eutectics solidified from undercooled states, in particular, within an individual eutectic colony and among neighboring eutectic colonies, have been measured with respect to the eutectic Ni3Sn and Ni phases; this was done using a scanning electron microscope equipped with the electron backscatter diffraction pattern (EBSP) mapping technique. The EBSPs and inverse pole figures indicate that the Ni3Sn intermetallic compound is continuous and well oriented whereas the Ni solid solution is discontinuous and randomly oriented within an anomalous eutectic grain. Further examination reveals that although Ni particulates are random from an overall view, most neighboring Ni grains have small misorientations of less than 10 degrees. The specific solidification sequence and the effect of released crystallization heat on subsequent crystallization are further considered, which enables the primary Ni phase to segment into individual grains whereas Ni3Sn does not due to higher entropy of fusion. A little rotation or floating within the constrained framework of the crystallizing Ni3Sn compound may yield small misorientation angles. The discontinuous Ni particulates and continuous Ni3Sn network are of great significance in revealing the anomalous eutectic formation. The orientation among independent eutectic colonies is random owing to the random appearance of nuclei throughout the volume of undercooled melts. The macrotextures of pole figures (PFs) of two eutectic phases are also mapped versus melt undercooling, which can be interpreted well when considering the nucleation frequency, variation of eutectic colony size, microtexture within a single eutectic colony, and the overall microstructure evolution as a function of melt undercooling.




90.    Li, M., T. Ishikawa, et al. (2005). "Experimental Evidence of Crystal Fragmentation from Highly Undercooled Ni99B1 Melts Processed on an Electrostatic Levitator." Metallurgical and Materials Transactions A 36A(11): 3254-3257A.

Employing an electrostatic levitator (ESL) equipped with a CO2 laser heating setup, we solidified Ni99B1 bulk crystals through containerless processing at high undercoolings and observed grain-refined microstructures. The electron backscatter diffraction pattern (EBSP) and analysis of the twin directions were accomplished, from which the primary growth traces with a cellular-like structure were revealed on a macro-millimeter scale. In comparison with the strong mechanical electromagnetic stirring in a sample processed on an electromagnetic levitator, the ESL provides a quite quiescent state for the melt, which enables identification of the primary growth traces after solidification. The present observation supplied experimental evidence that the refined microstructure in the Ni99B1 alloys at the high undercooling regime was due to fragmentation of the primary growth crystal, rather than dynamic nucleation.




91.    Li, M., Y. Ping, et al. (2004). An OIM Analysis on the Deformation Mechanism in Hot Compressed AZ31 Magnesium Alloy. International Conference on Magnesium – Science, Technology and Applications, Beijing, China, TransTech Publications.

Orientation mapping based on EBSD technique was applied to analyze the rules of orientation evolution of grains in AZ31 magnesium alloy. Results show that not only under deformation strain rate of 1*10-2 s-1, but under 4*10-4 s-1 (the superplastic deformation condition), grains in all samples with initial textures rotate gradually to near basal orientation ({0002}. compression plane) at different ways, and basal texture becomes stronger with increasing strain, which indicates plastic slip plays an important role during hot deformation. Otherwise, no evident non-basal pyramidal slip of <a+c> as some studies mentioned was observed in the sample with the initial basal texture, and the basal orientation is kept unchanged during the deformation process, which suggests that basal slip is the uppermost plastic slip mechanism in this sample. In addition, the phenomenon of viscous laminar flow was observed in the sample with initial basal texture.




92.    Li, S., I. J. Beyerlein, et al. (2004). "Heterogeneity of deformation texture in equal channel angular extrusion of copper." Acta Materialia 52(16): 4859-4875.

Texture evolution and heterogeneity during equal channel angular extrusion (ECAE) of an annealed pure copper billet are investigated using a combined finite element-polycrystal modeling approach. For the first ECAE pass, texture predictions at several locations across the billet using either the visco-plastic self consistent (VPSC) or Taylor model are compared against orientation imaging microscopy (OIM) texture measurements. The results show significant spatial variation in texture, in good agreement with the OIM measurements, and indicate a better performance of the VPSC model than the Taylor model. The study was extended for routes A and C up to 16 passes. For route A the textures at the top and middle regions are similar, remain much stronger than that in the bottom region, and strengthen with the number of passes. In route C, the textures at the top and bottom positions become similar after the second pass, but are quite different from the textures in the middle; the texture heterogeneity is smaller for odd-numbered passes than for even-numbered passes.




93.    Li, S., I. J. Beyerlein, et al. (2005). "Texture formation during equal channel angular extrusion of fcc and bcc materials: comparison with simple shear." Materials Science and Engineering A 394(1-2): 66-77.

The texture formation in one pass of equal channel angular extrusion (ECAE) is investigated in comparison with that after simple shear deformation. The orientation of the die's intersection plane and the deviation of deformation from simple shear along this plane are the two main factors that together contribute to differences in measured ECAE textures from simple shear. With this in mind, an appropriate method for analysis of ECAE textures is developed. Using an idealized simple shear model for ECAE deformation, the ideal orientations and fiber textures for ECAE of both fcc and bcc materials are derived for any die angle. To demonstrate this method, two popular polycrystal models, finite element simulation, and orientation imaging microscopy texture measurements of copper are used to quantify the individual contributions of these two factors in actual ECAE deformation. The importance of comparing ECAE textures with the negative rather than positive shear texture is emphasized, otherwise interpretations of the ECAE experimental and simulated data can be misleading.




94.    Li, S., I. J. Beyerlein, et al. (2005). "Texture formation during equal channel angular extrusion of fcc and bcc materials: comparison with simple shear." Materials Science and Engineering A 394: 66-77.

The texture formation in one pass of equal channel angular extrusion (ECAE) is investigated in comparison with that after simple shear deformation. The orientation of the die’s intersection plane and the deviation of deformation from simple shear along this plane are the two main factors that together contribute to differences in measured ECAE textures from simple shear.With this in mind, an appropriate method for analysis of ECAE textures is developed. Using an idealized simple shear model for ECAE deformation, the ideal orientations and fiber textures for ECAE of both fcc and bcc materials are derived for any die angle. To demonstrate this method, two popular polycrystal models, finite element simulation, and orientation imaging microscopy texture measurements of copper are used to quantify the individual contributions of these two factors in actual ECAE deformation. The importance of comparing ECAE textures with the negative rather than positive shear texture is emphasized, otherwise interpretations of the ECAE experimental and simulated data can be misleading.




95.    Li, S., I. J. Beyerlein, et al. (2006). "On the development of microstructure and texture heterogeneity in ECAE via route C." Acta Materialia 54(5): 1397-1408.

Deformation in every two passes of route C by equal channel angular extrusion (ECAE) is commonly viewed as severe forward and reverse shearing. Contrary to predictions by standard polycrystal models, microstructural observations and texture measurements of a variety of ECAE materials consistently show that the initial state of the material is not recovered after even-numbered passes in this route. For the first time, the factors governing the microstructural and texture evolutions during two passes of route C are investigated using orientation imaging microscopy (OIM) and multi-scale modeling. For a two-pass pure copper sample processed by a 90° die, a useful model example, the OIM measurements reveal that the variation in microstructure and texture across the sample thickness is significant and all the textures show shear-type characteristics. Using finite element simulations for the macroscopic deformation, self-consistent modeling for polycrystals, and a latent hardening model for single crystals, it is shown that the deviation from idealized simple shear deformation and the difference in the deformation between successive passes due to changes in material behavior play a primary role, while anisotropy in single-crystal hardening plays a relatively minor one. Textures predicted, considering the two main factors, are in good agreement with the measurements.




96.    Li, S., R. A. Varin, et al. (2004). "Controlled mechano-chemical synthesis of nanostructured ternary complex hydride Mg2FeH6 under low-energy impact mode with and without pre-milling." Journal of Alloys and Compounds 384(1-2): 231-248.

The nanostructured ternary complex hydride Mg2FeH6 has been successfully synthesized in the present work by controlled reactive mechanical alloying (CRMA) of elemental Mg and Fe powders under low-energy impact mode in the magneto-mill Uni-Ball-Mill 5. The average nanograin (crystallite) size of Mg2FeH6 is within the range of ~2–6 nm as estimated by XRD. The highest yield of Mg2FeH6, close to ~34 wt.% as determined by XRD and DSC, is observed after 270 h of direct (no pre-milling) CRMA. The formation of MgO during CRMA is identified as the primary factor that greatly hinders the initial formation of Mg2FeH6. Pre-milling of elemental Mg–Fe mixture can accelerate formation of Mg2FeH6 but the pre-milling time has not yet been optimized in the present work. The persistent presence of unreacted Fe even after CRMA for as long as 370 h is observed in all powders synthesized in this work. DSC hydrogen desorption temperatures obtained in the present work are much lower than those reported by other researchers for the Mg–Fe–H system. These desorption temperatures (onset and peak) are close to or substantially lower than 300 °C irrespective of whether the desorbing hydride is either ß-MgH2 or Mg2FeH6 although it must be noted that the lowest DSC desorption peak temperature is associated with the hydrogen desorption from Mg2FeH6. Hydrogen desorption peak temperatures determined by thermally programmed desorption (TPD) are, on average, at least 50 °C lower than those determined by DSC. Within the range of ~1 to ~10 nm nanograin (crystallite) size of ß-MgH2 and Mg2FeH6 no systematic correlation is observed between the DSC and TPD desorption peak temperatures of both hydrides and their nanograin sizes.




97.    Li, T., A. M. Scotch, et al. (1998). "Single Crystals of Pb(Mg1/3Nb2/3)O-3-35 Mol-Percent PbTiO3 from Polycrystalline Precursors." Journal of the American Ceramic Society 81(1): 244-248.




98.    Li, X. L., W. Liu, et al. (2005). "EBSD analyses on recovery and recrystallization of high purity cold rolled nickel." Chinese Journal of Stereology and Image Analysis 10(4): 221-224.

High purity nickel rolled to a reduction of 98% was annealed for different temperatures and times. The recovery and recrystallization of the nickel during annealing was investigated by the electron backscatter diffraction technique in the scanning electron microscope. The results show that recovery and nucleation begin at 220°C. With increasing annealing temperatures and/or times, the recrystallization continues to completion. During annealing, the cube-oriented grains grow to dominate the microstructure.




99.    Li, X., W. Liu, et al. (2005). Cube texture development in pure Ni during annealing in a high strength magnetic field. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.

A 10 Tesla magnetic field was applied during annealing of cold-rolled high purity Ni at 300°C for 2 hours, with samples aligned at various different angles to the magnetic field direction. The effect of the magnetic field annealing on the cube texture evolution and the microstructural development was investigated by use of electron backscatter pattern (EBSP) analysis in the scanning electron microscope. The results show that both the cube texture evolution and the grain size are affected by the application during annealing of a high strength magnetic field, and that the effect varies as a function of the angle between the sample normal and the magnetic field direction. The cube texture volume fraction resulting from 2 hours annealing increases with increasing angle between the field direction and the sample normal direction, though in nearly all cases lower cube volume fractions were obtained compared to annealing without a magnetic field. The average size for all grains and for just cube-oriented grains both decrease with decreasing cube texture fraction, suggesting that the presence of a magnetic field either leads to enhanced recrystallization nucleation, or to a retardation of grain growth after recrystallization.




100.    Li, Z. J. and Q. Liu (2002). "Microstructure and local crystallography of rolled Al-1wt%Mn single crystals of {001} <110> orientation." Materials Science and Engineering A 338(1-2): 237-242.

Al–1wt%Mn single crystals of {001}<110> orientation have been rolled to 30 and 50% reductions under controlled homogeneous rolling conditions. The local orientations have been measured by the electron back-scattered pattern (EBSP) technique and a semi-automatic TEM method over different scales. EBSP orientation image maps (OIMs) based on the local orientation data and TEM micrographs were used to reveal the deformation structure. It was found that the crystals subdivided into different macroscopic regions across the specimen thickness and significant microstructural difference was observed in regions with different macroscopic orientations. Good agreement was revealed by comparison of the results concerning microstructure and local crystallography obtained from EBSP and TEM measurement.




101.    Li, Z. J., A. Godfrey, et al. (2001). "Macroscopic sub-division of rolled Al-1%Mn single crystals of 110 orientation." Scripta Materialia 45(7): 847-52.




102.    Li, Z. J., A. Godfrey, et al. (2004). "Evolution of microstructure and local crystallographic orientations in rolled Al–1%Mn single crystals of {0 0 1}<110> orientation." Acta Materialia 52: 149-160.

Al–1%Mn single crystals of {0 0 1}<110> orientation, rolled to reductions of between 18% and 90%, were examined using transmission and scanning electron microscope techniques, in order to examine the crystal subdivision pattern over both macroscopic and microscopic length scales. Deformation resulted in a macroscopic subdivision across the specimen thickness into three types of region – matrix regions, transition regions, and a central region consisting of two sharply alternating, highly misoriented, orientations. Significant differences, both in the microstructure and local crystallography, were observed in each of the three types of region. A model linking the location-dependent distortion tensor to the crystal rotation via the slip amplitudes was able to account for the observed pattern of crystal rotations, except for in the central region of each sample. The assumption used in the model of imbalanced slip on two sets of coplanar systems was supported by an analysis, using the Frank formula, of dislocation boundary content.




103.    Li, Z. J., G. Winther, et al. (2004). "Anisotropy of plastic deformation in rolled aluminum." Materials Science and Engineering A 387-389: 199-202.

Tensile properties were investigated along different directions in rolled sheets of recrystallized commercial purity aluminum. The dependence of the flow stress anisotropy on the prestrain level was analyzed in relation to the evolution of the dislocation structure during rolling. The anisotropy of the stress–strain behavior at a prestrain of 0.17 was studied. It is found that the directionality of the planar dislocation boundaries formed during prestraining gives a major contribution to the anisotropic plastic behavior. The magnitude of this contribution depends on the prestrain, which controls the boundary spacing and misorientation.




104.    Li, Z. J., G. Winther, et al. (2005). Flow Stress Anisotropy − Effect of Microstructure and Texture in Aluminium and IF steel. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.

The effect of microstructure and texture on the flow stress anisotropy in aluminium and IF steel has been investigated. The samples are recrystallized commercial purity aluminium (AA1050) cold rolled to prestrains of 0.05, 0.11 and 0.2, and recrystallized IF steel cold rolled to a prestrain of 0.28. The flow stress anisotropy was measured by tensile testing of specimens cut along different directions in the rolling plane. Pronounced anisotropy was found in both materials in spite of weak textures. The yield stress increases with increasing angle between the tensile direction and the rolling direction at all prestrains. The effect of microstructure and texture on the flow stress anisotropy was modelled by incorporating into a full-constraint Taylor model the strengthening effect of dislocation boundaries. The modelling and experimental results agree well, leading to a discussion of effect of the microstructure and texture on the flow stress anisotropy.




105.    Li, Z. J., Q. Liu, et al. (2002). Local Texture Evolution during Rolling Deformation of Single Crystals of {100}<011> Orientation. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.

Single Crystals of the 45°ND rotated cube orientation, {100}<011>, are very unstable under rolling deformation, and therefore are expected to provide a good system for investigating the effect of location dependent shear strain on texture evolution during rolling. For this purpose, single crystals of Al-1%Mn have been deformed by cold rolling to reductions of up to 90%. The macroscopic pattern of crystal rotation across the thickness of the samples has been investigated using orientation measurements obtained using the electron back-scattered pattern (EBSP) technique. Analysis of the microscopic sub-division pattern was carried out both using EBSP measurements together with transmission electron microscope (TEM) investigations. Similar to observations made on rolled single crystals of the {100}011> orientation, extended regions of either continuously varying orientation (transition bands), and regions of orientation (matrix bands) are observed. Additionally in the central layer of the rolled sample, a region consisting of narrow layers with orientations alternating between just two texture components, was observed at all strains. This complex pattern of macroscopic crystal rotations is related to the total external imposed shear strain resulting both from geometrical and frictional effects.




106.    Likhachev, V. A., M. M. Myshlyayev, et al. (1987). "On Role of Structure Transformations in Superplasticity." Fizika Metallov I Metallovedenie 63(6): 1045-1060.




107.    Lill, K. A., A. W. Hassel, et al. (2005). "Scanning droplet cell investigations on single grains of a FeAlCr light weight ferritic steel." Electrochimica Acta 51: 978-983.

Polycrystalline Fe7.5Al7Cr is a ferritic light weight steel that shows a strong anisotropic dissolution behaviour. This electrochemical phenomenon was investigated by use of a scanning droplet cell (SDC). The crystallographic orientation of the single grains was determined by electron back scatter diffraction (EBSD). The fraction of grains with a near <1 1 1> orientation (<10°) was 1.88 times higher than that of the near <0 0 1> orientation prior to annealing and 3.58 times higher after annealing. Voltammograms were performed on single grains with low index planes. The critical current density was 53% higher on <0 0 1> grains as compared to <1 1 1> grains. These results are used to discuss the electrochemical behaviour of the polycrystalline FeAlCr.




108.    Lillywhite, S. J. (2000). Prediction of Texture Development in Aluminium. Thermec 2000, Las Vegas, Nevada, USA, Elsevier Science Ltd.

Aluminium bicrystals and single crystals of various initial orientations were deformed by channel die compression and the orientation evolution during deformation was investigation by EBSD on the SEM. It was found that experimental bicrystals did not necessarily exhibit behaviour that was similar to single crystals of the same orientation. A Crystal Plasticity Finite Element Modelling (CPFEM) program was used in an attempt to predict the microstructures that developed in the experimental specimens. Although some model predictions of the experimental behaviour were accurate, some were less so. It is suggested that this is due to the influence of dislocations and substructure on the lattice rotations that cause the orientation evolution during deformation. In addition, a large range of orientations were investigated by a simple Taylor test, by CPFEM as bicrystals with dies, as single crystals with dies and as single crystals under relaxed constraints. The results showed that CPFEM with dies gives a more realistic spread of orientations compared to the experimental results.




109.    Lillywhite, S. J., A. J. Williams, et al. (2002). "A preliminary electron backscattered diffraction study of sintered NdFeB-type magnets." Journal of Microscopy 205(3): 270-277.

This paper reports, for the first time, the use of electron backscattered diffraction (EBSD) to study orientation in sintered NdFeB type magnets. The magnetic properties of NdFeB magnets are greatly improved if a strong crystallographic texture is firstly achieved, namely, the direction of the c-axis is along the direction of magnetization. A systematic survey of sample preparation techniques showed that samples that were mechanically polished and then etched gave the most reliable EBSD data. Analyses were made using both fully automated EBSD scans and by EBSD measurements taken after manual movement of the beam. The EBSD results are presented as secondary electron SEM micrographs, orientation images and 001 pole figures. For the selection of grains investigated, the deviation of the c-axis was shown to be between 10° and 30° from the ideal [001]//magnetization direction. It is demonstrated that EBSD is a valuable tool for characterizing the microstructure and texture relationships and for assessing the performance of the processing routes of NdFeB magnets.




110.    Lillywhite, S. J., A. J. Williams, et al. (2002). Magnetic Alignment and Crystallographic Texture Relationships in Permanent NdFeB Magnets. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.

This paper reports on an Electron Backscattered Diffraction (EBSD) investigation of two fully dense sintered magnets with differing degrees of crystallographic alignment. The relationship between magnetic alignment and crystallographic texture is demonstrated by comparing with ideal single phase single crystals and the quality of each magnet in terms of crystallographic alignment is determined. It is suggested that for orientations where the <001> zone axis is not visible in the Kikuchi pattern, then it is more difficult to assign an orientation.




111.    Lillywhite, S. J., M. Aindow, et al. (1999). G rain boundary influence on texture evolution during deformation and recrystallization. Twelfth International Conference on Textures of Materials (ICOTOM 12), McGill University, Montreal, Canada, NRC Research Press.




112.    Lim, J. H., K. T. Kim, et al. (2006). "Development of textured Ni substrates prepared by powder metallurgy and casting." Physica C 436(2): 103-109.

We fabricated the textured Ni substrate for YBCO coated conductors and evaluated the effects of processing variables on microstructural evolution and texture transformation. Initial specimens were prepared by two different methods, i.e., powder metallurgy (P/M) and casting. To characterize the role of two preparation methods, the initial specimens of the same size were prepared under the same rolling and annealing conditions. The microstructure and texture were evaluated by orientation distribution function (ODF), electron backscattering diffraction and transmission electron microscopy with selected area diffraction. We observed that the microstructure of the rolled tape varied with preparation methods; the rolled tape prepared by P/M had more deformation bands and stronger β-fiber texture than that one obtained by casting, resulting in finer microstructure and stronger cube texture after recrystallization. The smaller grains in the former tape were explained by the “variation inhibition theory” together with in situ TEM result. Texture analysis indicated that the substrate made by P/M had a stronger cube texture and a wider annealing temperature range in which the cube texture became stable, compared to that of the casting-substrate. In addition, abnormal grain growth occurred and consequently formed high angle grain boundary for substrate by casting but not for substrate by P/M.




113.    Lim, L. C. and R. Raj (1984). "Effect of Boundary Structure on Slip-Induced Cavitation in Polycrystalline Nickel." Acta Metallurgica 32(8): 1183-1190.




114.    Lim, L. C. and R. Raj (1984). "On the Distribution of Sigma for Grain-Boundaries in Polycrystalline Nickel Prepared by Strain-Annealing Technique." Acta Metallurgica 32(8): 1177-1181.




115.    Lim, L. C. and R. Raj (1985). "Continuity of Slip Screw and Mixed-Crystal Dislocations Across Bicrystals of Nickel at 573-K." Acta Metallurgica 33(8): 1577-1583.




116.    Lim, L. C. and R. Raj (1985). "Interaction Between Lattice and Grain-Boundary Dislocations and Their Role in Mechanical-Properties of Interfaces." Journal de Physique I 46(NC-4): 581-595.




117.    Lin, D. and F. Sun (2004). "Superplasticity in a large-grained TiAl alloy." Intermetallics 12(7-9 (Special Issue)): 875-883.

The superplastic behaviour was systematically investigated in a large-grained Ti-47Al-2Mn-2Nb-B alloy having nearly equiaxed g-phase with grain size of 95 µm, in which a small amount of fine particles of α2 distribute uniformly. Superplastic deformation was examined at a temperature range of 1025-1100 °C and strain rates range of 4x10-5-1.28x10-3s-1. The large-grained TiAl alloy exhibits all deformation characteristics of conventionally fine-grained superplastic alloys without the prerequisites, fine grain size and grain boundary sliding. All the values of strain rate sensitivity, m are larger than 0.3. In most cases, an elongation over 200% was gained. A maximum elongation of 287.5% with an m value of 0.39 was obtained at 1100 °C and an initial strain rate of 4x10-5s-1. Microstructure evolution during superplastic deformation was characterized by optical microscopy, orientation imaging microscopy and transmission electron microscopy (TEM). Metallographic examination has shown that the average grain size of large-grained TiAl alloy decreased during superplastic deformation, after that a much finer grain size of 10 to 3-5 µm could be obtained. Electron back-scattered diffraction analysis revealed that significant grain refinement was obtained at different levels with an increase in the density of low and high angle grain boundaries. A direct evidence for dynamic formation of grain boundaries with misorientation of 15-30° was found, which was evolved from subboundaries. The evidence of subboundary formation and dislocation glide in the interior of grains was revealed by TEM observation. A continuous recovery and recrystallization process similar to that in FeAl and Fe3Al alloys was proposed as the superplastic deformation mechanism in the large-grained TiAl alloy.




118.    Lin, D. and J. Hu (2003). Superplasticity in Large-Grained Intermetallics. Thermec' 2003, Leganés, Madrid, Spain, Trans Tech Publications Ltd.

Superplastic behavior has been found in Fe3Al, Fe3Si, FeAl, Ni3Al, NiAl and TiAl alloys with large grain sizes (>30-600 µm). The large grain intermetallic alloys exhibit all deformation characteristics of fine grained superplastic alloys without the usual pre-requisites of a fine grain size and grain boundary sliding. Metallographic examination has shown that the average grain size of a large grain intermetallic decreased during superplastic deformation and a much finer grain size could be obtained aftrer superplastic deformation. Transmission electron microscopy (TEM) and orientation electron microscopy (OIM) observations have shown that there were great numbers of subgrain boundaries which formed a network and among which the proportion of low and high angle boundaries increased with the increase of strain. The observed superplastic phenomenon is explained by continuos dynamic recovery and recrystallization (CDRR).




119.    Lin, D., J. Hu, et al. (2005). "Superplasticity of Ni-rich single phase NiAl intermetallics with large grains." Intermetallics 13(3-4): 343-349.

Superplastic behavior has been found in Ni-rich single phase NiAl intermetallics with large grains. The large-grained NiAl alloy exhibited deformation characteristics of most fine-grained superplastic alloys without the usual pre-requisites of a fine grain size and grain boundary sliding. Metallographic examination (OM) showed that the average grain size of large-grained NiAl alloys decreased during superplastic deformation and a much finer grain size was obtained after superplastic deformation. Transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD) observations showed that there were great numbers of subgrain boundaries which formed a network and among which the proportion of low and high angle boundaries increased with the increase of strain. The maximum elongation to fracture increases with the increase of Ni content in Ni-rich single phase NiAl intermetallics. The observed superplastic phenomenon is explained by continuous dynamic recovery and recrystallization. Copyright 2004 Elsevier Ltd. All rights reserved.




120.    Lin, F., A. Godfrey, et al. (2004). Monte Carlo Modeling of Cube Texture Evolution in Ni-Tapes during Grain Growth. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.

After primary recrystallization of highly rolled (> 98% reduction) high purity Ni (99.999%) tapes the cube texture fraction can range from 45-65%. Annealing at temperatures > 1000DGC leads to cube texture volume fractions of > 95% as a result of grain growth. A Monte Carlo Potts model was used to simulate this annealing process. The starting microstructures for the simulations were generated from experimental data taken using electron backscatter pattern analysis. The simulation results suggest that in addition to the grain boundary misorientation and energy functions used, the misorientation texture and grain sizes are also determining factors in the grain growth process. As the grain size after recrystallization is comparable to the tape thickness, the surface energy of the grains may also be an important factor. Simulations were therefore also carried using a surface energy term. If the cube grains have a lower surface energy then a stronger cube texture is predicted. (Application: YBCO superconductor substrates.)




121.    Lin, H. and D. P. Pope (1993). "The Influence of Grain-Boundary Geometry on Intergranular Crack-Propagation in Ni3Al." Acta Metallurgica et Materialia 41(2): 553-562.

The distribution of grain boundary types along intergranular cracks in Ni3Al was measured, by Σ value, and compared to the distribution in the bulk, using statistically significant sample sizes. It was found that low angle (Σ1) and symmetrical Σ3 boundaries (twins) are particularly strong, and all high angle boundaries, independent of their Σ values are weak. In particular, low Σ, high angle boundaries, as a group, are also weak. These results are in qualitative agreement with predictions based on the structural unit model and imply that the fracture strength of an intergranularly brittle polycrystalline aggregate can be increased only by increasing the fraction of low angle and symmetrical Σ3 boundaries.




122.    Lin, H. and D. P. Pope (1994). Slip traces caused by plastic deformation during recrystallization of thin metal sheets. Fifty-Second Annual Meeting Microscopy Society of America/Twenty-Ninth Annual Meeting Microbeam Analysis Society, New Orlean, LA, San Francisco Press, Inc.

During a study of mechanical properties of recrystallized B-free NiAl single crystals, regularly spaced parallel traces within individual grains were discovered on the surfaces of thin recrystallized sheets. They appear to be slip traces. A series of experiments was performed to identify them. A variety of techniques, including the Electron Backscattering Pattern (EBSP) method was used to ascertain the composition, geometry, and crystallography of these traces. The effect of sample thickness on their formation was also investigated. [References: 5]




123.    Lin, H. and D. P. Pope (1994). "Texture and Grain-Boundary-Character-Distribution in Recrystallized Ni3Al Sheets." Scripta Metallurgica et Materialia 30(11): 1409-1412.




124.    Lin, H. and D. P. Pope (1995). "Formation of Slip Traces During Recrystallization of Thin Metal Sheets." Philosophical Magazine A 71(6): 1241-1253.




125.    Lin, H. and D. P. Pope (1995). "Weak Grain-Boundaries in Ni3Al." Materials Science and Engineering A 193: 394-398.




126.    Lin, P., G. Palumbo, et al. (1995). "Influence of Grain-Boundary-Character-Distribution on Sensitization and Intergranular Corrosion of Alloy-600." Scripta Metallurgica et Materialia 33(9): 1387-1392.




127.    Lin, P., G. Palumbo, et al. (1997). "Experimental Assessment of the Contribution of Annealing Twins to Csl Distributions in fcc Materials." Scripta Materialia 36(10): 1145-1149.




128.    Lin, Z. R., T. G. Langdon, et al. (1988). "An Investigation of Grain-Boundary Sliding in Superplasticity at High Elongations." Journal of Materials Science 23(8): 2712-2722.




129.    Lineau, C., C. Rey, et al. (1997). "Experimental analysis of plastic deformation of steel grains: Comparison with polycrystal models predictions." Materials Science and Engineering A 234-236: 853-856.




130.    Lingk, C., M. E. Gross, et al. (2000). "Texture Development of Blanket Electroplated Copper-Films." Journal of Applied Physics 87(5): 2232-2236.




131.    Lins, J. F. C., H. R. Z. Sandim, et al. (2005). An EBSD Investigation on Deformation-Induced Shear Bands In Ti-Bearing IF-Steel Under Controlled Shock-Loading Conditions. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.

We report the results of the microstructural characterization of a Ti-bearing IF-steel deformed at high strain rates (≈ 6.104 s-1) in a split Hopkinson bar. The shock-loading tests were performed in hat-shaped specimens to induce the formation of adiabatic shear bands (ASB). The samples were peformed at 223 K and 298 K. High-resolution electron backscatter diffraction (EBSD) reveals the development of an ultrafine-grained structure within the ASB. A closer inspection reveals the presence of deformation twins in grains adjacent to the shear band. These twins bend towards the ASB suggesting that mechanical twinning occurs before the flow associated to shear banding. The results of microtexture have indicated the presence of a sharp <111> γ-fiber texture in the ASB for both temperatures.during the 923K biaxial rolling.




132.    Lippold, J. C. and M. Qian (2002). The Effect of Grain Boundary Character Distribution on the Repair Weldability of Waspaloy. Trends in Welding Research: Proceedings of the 6th International Conference, Phoenix, Arizona, USA.

Wrought Waspaloy was found to become more susceptible to heat-affected-zone (HAZ) liquation cracking after a 1079 degrees C/40hr long-term, isothermal heat treatment that was used to simulate multiple post weld heat treatment (PWHT) cycles that are applied following repair welding. This degradation in weldability was associated with the increase in grain size that occurs with prolonged elevated temperature exposure. The increased susceptibility to liquation cracking was most pronounced in a forged Waspaloy turbine disk. Increasing the elevated temperature exposure at 1079 degrees C from 40 to 100 hrs was found to restore the weldability of the Waspaloy disk to the level of the original forging, even though the grain size was comparable to that of the 40hr-treated material. This improvement is associated with the high volume fraction of twin boundaries, and corresponding special GBs in the 100hr-treated microstructure. The combined effect of grain size and fraction of special grain boundaries on HAZ liquation cracking is discussed on the context of GB engineering concepts.




133.    Lischewski, I. and G. Gottstein (2005). In-Situ Investigation of Transformation Textures in Microalloyed Steels. Solid to Solid Phase Transformations in Inorganic Materials 2005, Phoenix, Arizona, USA, TMS.

The texture evolution during the a-g phase transformation in a microalloyed steel was studied. For texture measurement of the high temperature austenite phase, an X-ray texture goniometer with a customized in-house built high temperature stage was utilized. This technique allows pole figure measurments up to 1000°C.

The local crystallography was measured by EBSD in a high resolution FEG-SEM. A special annealing treatment enabled stabilization of the high temperature austenite phase. By determination of the microstructure and local orientation before and after the phase transformation at the same location, it is possible to establish a direct crystallographic correspondence between prior and subsequent phase. This can be utilized for information on the mechanisms of phase transformation and the influence of twinning on the transformation texture.




134.    Lischewski, I. and G. Gottstein (2005). Orientation Relationship during partial α-γ-Phase Transformation in Microalloyed Steels. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.

The ferrite to austenite phase transformation in microalloyed steel was studied, with a special focus on the orientation relationship between prior ferrite and subsequent austenite. Also the role of growth selection and preferred nucleation was investigated in this context. Their effects were examined at partial phase transformation.




135.    Lita, A. E. and J. E. Sanchez (2002). "Effect of the Underlayer on the Microstructure and Surface Evolution in Al-0.5wt%Cu Polycrystalline Thin Fims." Journal of Electronic Materials 31(1): 55-65.

The effects of theTi underlayer on the evolution of grain morphology, crystallographic texture, and surface roughness of Al-0.5wt.%Cu thin films during sputter deposition have been characterized. In comparison to SiO2substrates, Ti underlayers reduce the AlCu thickness at which film continuity is reached, reduce the AlCu columnar grain size, and allow exact Al(111) fiber texture development. The AlCu films on both Ti and SiO2 are primarily randomly oriented at early stages of deposition. A near -(111) Al fiber texture in AlCu/SiO2 films initiates during the preferential growth of 5° offset islands prior to film continuity, seeding the near Al(111) texture as film continuity is reached. The exact Al(111) fiber orientation in AlCu/Ti films develops after film continuity. The near -(111) and exact (111) fiber textures strengthen with further deposition due to combined normal and abnormal grain groowth. Film coalescence and grain growth lead to a significant smoothing effect during the early stages of deposition.




136.    Liu, D., H. V. Atkinson, et al. (2005). "Disagglomeration in thixoformed wrought aluminium alloy 2014." Materials Science and Engineering A 392(1-2): 73-80.

Thixoforming is a type of semi-solid metal processing, which involves the processing of alloys in the semi-solid state. Disagglomeration of solid globules during thixoforming of wrought aluminium alloy 2014 was investigated by electron back-scatter diffraction. The recrystallisation and partial melting route was used to produce the thixotropic feedstock for thixoforming. The starting material was commercially extruded wrought aluminium alloy 2014 in the T6 temper condition. The crystallographic orientations of the grains and misorientation between neighbouring grains were investigated in the starting material, isothermally heat-treated material (heat treated at temperatures up to 901 K to mimic the treatment which the thixoformed sample undergoes prior to forming) and in as-thixoformed material. The starting material showed strong{1 1 0}<3 2 2> and {1 1 2}<1 1 1? components, which were replaced by strong {1 0 0}<0 0 1> texture during heat treatment. Thixoforming of the material almost completely randomised the texture, indicating that disagglomeration has occurred. About a quarter of the boundaries in the as-received material are low angle grain boundaries. This declines to about 18% in the heat-treated but the as-thixoformed misorientation data suggests a very high proportion of LAGBs. This is thought to be an artefact associated with the fact that the EBSD programme is attempting to resolve the microstructure within what was liquid and to allocate orientations within that. The data do not represent the parameter which is sought viz. the misorientation between what were neighbouring solid spheroids in the semi solid state because these are now separated by solidified liquid. The data on misorientation in systems which have been semi-solid must therefore, be treated with circumspection. Copyright 2004 Elsevier B.V. All rights reserved.




137.    Liu, D.-M., W.-P. Liu, et al. (2005). Texture Control in Silver. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.

The influence of the oxygen-content, the rolling method, the annealing method and the annealing temperature on the texture in silver have been studied. The results show that low oxygen-content in original material, annealing at a temperature higher than 700°C and annealing in an atmosphere such as inert gas, air or pure oxygen are beneficial to obtain the {110}<110> component. Textured Ag substrate in which the main components is {110}<110> has been obtained. The mechanism of texture-forming is studied using electron back-scattered diffraction (EBSD) method.




138.    Liu, J. and D. J. Chakrabarti (1996). "Grain-Structure and Microtexture Evolution During Superplastic Forming of A High-Strength Al-Zn-Mg-Cu Alloy." Acta Materialia 44(12): 4647-4661.

Grain structure and microstructure evolution during superplastic forming were studied on an unrecrystallized sheet of a modified 7050 superplastic alloy. A SEM-based local orientation technique was used to cover a large number of (sub)grain boundaries in combination with other metallographic techniques. The gradual boundary misorientation and microtexture evolution during superplastic forming (SPF) confirmed that a continuous evolutionary process was occurring. There was no evidence of dynamic recrystallization at the stress maximum. The fraction of high angle boundaries increased rapidly once the mean misorientation reached a critical value. These and other results suggest that both grain boundary sliding (GBS) and dislocation slip were operative initially until the stress maximum was approached, beyond which GBS was predominant. The results of quantitative orientation distribution function (ODF) analyses suggest that grain rotation, which resulted in texture randomization, became important from slightly beyond the stress maximum through most of the stress-strain curve.




139.    Liu, J. and J. G. Morris (2003). "Texture and Grain-Boundary Evolutions of Continuous Cast and Direct Chill Cast AA 5052 Aluminum Alloy during Cold Rolling." Metallurgical and Materials Transactions A 34A(4): 951-966A.

Commercially produced hot bands of continuous cast (CC) and direct chill (DC) cast AA 5052 aluminum alloy were cold rolled to different reductions from 10 pct through 90 pct. Evolution of deformation textures in the CC and DC materials was investigated by using three-dimensional orientation distribution functions (ODFs) that were determined by X-ray diffraction. The electron backscatter diffraction (EBSD) technique was adopted to keep track of the evolution of grain boundaries of CC and DC materials during the early stages of cold rolling (<=40 pct thickness reduction). Results showed that the Cube cluster is found in annealed DC hot band. A much stronger Cube orientation is found in DC hot band than inCC hot band. The cold rolling texture evolutions for CC and DC materials follow the same path. The alpha and beta fibers become well developed after 60 pct cold rolling in both CC and DC materials. The highest intensity along the beta fiber (skeleton line) is located near the S orientation {123}<634> in both materials. There exists a path by which the copper orientation (112) 111 develops at the expense of the Cube orientation (001) 010 with an increase in cold rolling reductions. Low-angle boundaries with misorientation angles between 1.5 and 5 deg are rapidly increased during the early stage of cold rolling. There is no evidence of the development of twin and twin-related boundaries in either CC or DC materials when the cold rolling reductions are less than 40 pct.




140.    Liu, J. and M. J. G. (2003). "Macro-, micro- and mesotexture evolutions of continuous cast and direct chill cast AA 3105 aluminum alloy during cold rolling." Materials Science and Engineering A 357(1-2): 277-296.

Industrially produced hot bands of continuous cast (CC) and direct chill (DC) cast AA 3105 aluminum alloy were cold rolled to different reductions from 10 to 90%. Macrotexture evolution of the deformation texture in the CC and DC materials was investigated by using three-dimensional orientation distribution functions (ODFs) that were determined by X-ray diffraction. The electron backscatter diffraction (EBSD) technique was adopted to investigate micro- and mesotexture during the early stages of cold rolling (<= 40%). Results showed that the macrotexture evolution for CC and DC materials during cold rolling follows the same path, alpha and beta fibers become developed beyond 50% cold rolling in both CC and DC materials. The highest intensity along the P fiber (skeleton line) is located between the Copper and the S orientations in both materials. There exists a path by which Cube orientation (001) 100 transforms to the Brass orientation (011) 211 through the CubeND orientation (001) 110 after certain cold rolling reductions. In both CC and DC materials, a cell structure develops with the indication of increasing coincidence site lattice (CSL) Sigma 1 boundaries during the early stages of cold rolling while high-angle boundaries (HABs) are randomized over the misorientation angle. There is no evidence for the development of twin boundaries in both CC and DC materials when the cold rolling reduction is less than 40%. Cold rolling texture itself is not responsible for the different recrystallization behaviors that cause different earing behaviors between CC and DC aluminum alloys.




141.    Liu, L., H. Nakayama, et al. (2004). "Microscopic observations of friction stir welded 6061 aluminum alloy." Materials Transactions 45(2): 288-291.

As the automotive industry trends towards increased use of aluminum, the friction stir welding process offers many potential benefits for joining of aluminum. In this study, the microstructure in friction stir welded 6061 aluminum alloy was observed by metallographic technique, electron backscatter diffraction pattern (EBSD) and optical microscopy. The microstructure in the heat affected zone (HAZ) was significantly different from that in a thermo-mechanically affected zone (TMAZ). EBSD indicated that many more low-angle grain boundaries in TMAZ, i.e., subgrains with a recovered granular structure, were observed than in HAZ. Friction heating and plastic flow during friction stir welding created fine recrystallized grains and recovered grains in the TMAZ. The friction stir welding process produced a softened region in the 6061 Al welded alloy. In the stir zone, equiaxed grains were created and the grain size was smallest in the bottom area.




142.    Liu, L., H. Nakayama, et al. (2004). "Microstructural evolution in friction stir welded 1050 aluminum and 6061 aluminum alloy." Materials Transactions 45(8): 2665-2668.

The microstructure of friction stir welded 1050 aluminum and 6061 aluminum alloy was observed by a metallographic technique, transmission electron microscopy, electron backscatter diffraction pattern and optical microscopy. In the stir weld zone, the microstructure of welded 1050 aluminum was significantly different from that of the welded 6061 aluminum alloy. In the case of welding 1050 aluminum, there was a comparatively uniform microstructure in the stir weld zone, not a wedge-shaped microstructure formed in a stir welded 6061 aluminum alloy. EBSD indicated that there was almost same fraction of low angle boundaries among the thermo mechanically affected zone in welded 1050 aluminum and 6061 aluminum alloy. In the stir weld zone, equiaxed grains were created and the grain size of 1050 aluminum was little larger than that of 6061 aluminum alloy, suggesting that precipitates pinning effect affects the dynamic recrystallization in the stir weld zone.




143.    Liu, L., H. Nakayama, et al. (2005). Microstructure of Friction Stir Welded 6061 Aluminum Alloy. 9th International Conference on Aluminium Alloys, Brisbane, Australia, Institute of Metals and Materials Australasia Ltd.

The variation in the microstructure of a friction stir welded 6061 aluminum alloy was observed by a metallographic technique, electron backscatter diffraction pattern (EBSD), optical microscopy and transmission electron microscopy (TEM). At a low rotation speed and travel speed, the center portion of stir weld zone is dominated by a region deformed with a wedge-shaped microstructure, particularly in the lower branches. EBSD and TEM indicated that many more low-angle grain boundaries were observed in thermo-mechanically affected zone (TMAZ), i.e., subgrains with a recovered grain structure. Friction heating and plastic flow during friction stir welding create fine recrystallized grains and recovered grains in the TMAZ. The friction stir welding produces a wedge-shaped portion and a softened region in the welded 6061 Al. In the stir zone, equiaxed grains were created and the grain size became very small in the bottom area.




144.    Liu, P. and C. Ulfvin (1999). "Characterization of Zirconium Alloys by Identification of Intermetallic Particles and Fully-Automatic Measurement of Particle-Size Distribution Using Secondary-Electron Imaging in Scanning-Transmission Electron -Microscope." Materials Science and Technology 15(11): 1317-1323.

In Al-SiCw composites containing <or=4 vol.% SiCw, a fairly accurate estimate of the grain size can be obtained by optical microscopy and SEM (ECC) with the use of anodized and mechanically polished specimen, respectively. The ECC method possesses better resolution than the optical microscopy technique. This is of importance when the grain size is of the order of a few microns. The EBSP can be produced from an electropolished surface. This technique has a resolution better than 1 mu m and allows high-angle boundaries to be identified. In Al-SiCw composites with 4-10 vol.% SiCw, when grains are large (>100 mu m), the structure can be observed by anodic etching and optical microscopy. A fine-grain structure, which is not possible to observe directly by other techniques, can be studied by the EBSP technique with bulk specimens prepared by ion milling, or by TEM with ion-milled thin foils. (17 References).




145.    Liu, Q. (2005). "EBSD technique and its applications in materials science." Chinese Journal of Stereology and Image Analysis 10(4): 205-210.

In this paper, the basic principle of electron back-scattering diffraction (EBSD) technique is introduced. The modern EBSD system, experimental conditions, spatial resolution, angular resolution, and post analysis of the data are also described in this paper. Finally, the applications of the EBSD technique in material science are discussed by using a few typical examples.




146.    Liu, Q., W. Q. Cao, et al. (2004). Microstructural Parameter-Based Characterization of Annealing Behaviour in Metals Deformed to High Strains. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.

The transition from discontinuous recrystallization to a continuous recovery process during annealing of aluminium deformed to high plastic strains has been investigated by following several different microstructural parameters. Samples were examined following equal channel angular extrusion (ECAE), accumulated roll bonding (ARB) and high-strain conventional rolling (HSCR). Local variations in the uniformity of coarsening have been characterized by an analysis of grain size distributions, obtained from electron backscatter pattern investigations. Except for at the lowest strains the distributions were not obviously bimodal. Methods of separating the distributions into two parts based on the mean value have therefore also been examined. The results suggest that the presence of a high fraction of high angle boundaries (> 15DG) in the microstructure may be a necessary but not sufficient condition for continuous recovery during annealing. The annealing behaviour can be related in part to the heterogeneity of the deformed microstructures, which can be pronounced even after strains of - 10 (ECAE). The presence of oxide particles in the ARB sample has a beneficial effect in limiting the grain growth.




147.    Liu, W. and J. N. DuPont (2005). "Direct Laser Deposition of a Single-Crystal Ni3Al-Based IC221 W Alloy." Metallurgical and Materials Transactions A 36A(12): 3397-3406.

Single-crystal (SX) nickel aluminide alloys have potential for structural applications where hightemperature strength and oxidation resistance are required. In this work, SX deposits of the Ni3Al-based IC221W alloy were produced on a SX Ni-base superalloy substrate by means of the laser-engineered net shaping (LENS) process. The microstructure of the deposits was characterized. The effects of processing parameters on the SX solidification in the melt pool and on the fabricability by LENS were investigated. A simple relationship between the ratio of the temperature gradient to the growth velocity and the processing parameters was derived, which can be used qualitatively to guide the proper selection of processing conditions to maintain the columnar dendritic growth during the laser deposition. On the basis of analyses and experiments, the effects of processing parameters on the susceptibility to stray grain formation and solidification cracking are discussed.




148.    Liu, Y. and X. Wu (2005). An EBSD study of the microstructural evolution during superplastic deformation of a fine-grained AZ31 magnesium alloy. Magnesium Technology 2005. Proceedings of the Symposium Sponsored by the Magnesium Committee of the Light Metals Division (LMD) of TMS with the International Magnesium Association, San Francisco, California, USA, Minerals, Metals & Materials Society.

An EBSD study of the microstructural evolution during superplastic deformation was conducted on a commercial AZ31 magnesium alloy sheet with initial grain size less than 21 mu m. Before deformation, a strong (0001) basal fiber texture existed in the as-received sheet. With deformation, it was found that the grain size increased depending on deformation temperatures, and the pre-existing fiber texture was not destroyed during deformation although obvious grain boundary sliding was observed. At 673 K, grain boundary sliding was the main deformation mechanism, while at 773 K, grain boundary sliding accommodated by slip is the main mechanism. Considering the existence of the strong basal fiber texture during deformation, the strengthening in <1120> direction observed from the pole figures indicated that, instead of slip on basal plane, slip along <a> direction on non-basal plane was very important.




149.    Liu, Y. and X. Wu (2006). "An Electron-Backscattered Diffraction Study of the Texture Evolution in a Coarse-Grained AZ31 Magnesium Alloy Deformed in Tension at Elevated Temperatures." Metallurgical and Materials Transactions A 37(1): 7-18.

Electron-backscattered diffraction (EBSD) has been used to investigate the texture evolution during tensile deformation at temperatures between 673 and 773 K of a coarse-grained commercial AZ31 magnesium alloy. A weak (0001) fiber texture was initially present in the hot-rolled magnesium alloy plate. The [0001] directions of the grains spread 0 to 45 deg around the normal direction (ND) of the magnesium alloy plate. This pre-existing weak texture evolved during tensile deformation into a strong texture close to the {0001} <1100>. The [0001] directions of the grains rotated toward the orientations perpendicular to the tension axis of the samples, indicating that the {0001} <1120> slip system appeared to be the most active slip system, especially in the early stages of deformation. The EBSD Schmid-factor analysis revealed that, however, with an increase in strain and the rotation of the (0001) slip plane, the {1122} <1123> slip system appeared to be more favorable. The {1100} <1120> and {1101} <1120> slip systems remained favored throughout the strains investigated, indicating that {1100} and {1101} are two important slip planes for cross slip using the <1120> slip vector. It is found that the misorientation across one coarse grain (as high as 38.2 deg) is accommodated by low-angle grain boundaries (LAGBs). The formation of these LAGBs may be an intermediate stage of the coarse grain refinement that occurred during deformation.




150.    Liu, Y. L. and N. J. Fei (1990). "Study of various techniques for grain-structure investigation in Al-Sicw composites." Materials Characterization 25(2): 241-250.

In Al-SiCw composites containing <or=4 vol.% SiCw, a fairly accurate estimate of the grain size can be obtained by optical microscopy and SEM (ECC) with the use of anodized and mechanically polished specimen, respectively. The ECC method possesses better resolution than the optical microscopy technique. This is of importance when the grain size is of the order of a few microns. The EBSP can be produced from an electropolished surface. This technique has a resolution better than 1 mu m and allows high-angle boundaries to be identified. In Al-SiCw composites with 4-10 vol.% SiCw, when grains are large (>100 mu m), the structure can be observed by anodic etching and optical microscopy. A fine-grain structure, which is not possible to observe directly by other techniques, can be studied by the EBSP technique with bulk specimens prepared by ion milling, or by TEM with ion-milled thin foils. (17 References).




151.    Liu, Y. L., H. Hu, et al. (1994). "Deformation and Recrystallization of a Channel Die Compressed Aluminum Bicrystal with (112) [111]/(123)[412] Orientation." Acta Metallurgica y Materialia 43(6): 2395-2405.




152.    Liu, Y., Y. L. Liu, et al. (1999). Texture and microstructure in DC cast and SC aluminum alloys. Twelfth International Conference on Textures of Materials (ICOTOM 12), McGill University, Montreal, Canada, NRC Research Press.




153.    Llana-Fúnez, S. and E. H. Rutter (2005). "Distribution of non-plane strain in experimental compression of short cylinders of Solnhofen limestone." Journal of Structural Geology 27: 1205-1216.

Axi-symmetric compression experiments on short cylinders (radius > length) have great potential for the investigation of different nonplane strain geometries. In such experiments strain geometry and intensity are heterogeneously distributed throughout the specimens due to the effects of friction at the contact surface between the pistons and the specimen. We ran a series of tests on Solnhofen limestone at constant confining pressure (200 MPa), temperature (600 °C) and displacement rate (5.2 x 10-6 m s-1), conditions at which this material deforms predominantly by crystal plasticity. Using shape and crystallographic preferred orientation (SPO and CPO) patterns of calcite grains, the latter measured by electron back-scattered diffraction techniques (EBSD), we can discriminate areas in the deformed specimens with distinct non-plane strain geometries. SPO and CPO patterns record differences in the orientation of the finite stretching direction with respect to the external reference frame. It is radial in the vicinities of the rigid loading pistons, but circumferential outside the periphery of the pistons. As shortening progressed, the middle part of the specimen was extruded with respect to the contacts with the rigid end pieces, imparting a noncoaxial component to the flow with a circumferential vorticity axis in both upper and lower halves of the specimen. This component was recorded in the microstructure as an asymmetric CPO. The aim of the experiments is to improve the interpretation of naturally deformed rock bodies when strain departs from plane strain conditions by using the CPO as a 3D kinematic indicator, providing not only shearing direction but also information about the shape in 3D of the strain ellipsoid.




154.    Llana-Fúnez, S., A. Marcos, et al. (2005). "Strain geometry in Concepenido eclogites during widespread HP deformation (Cabo Ortegal Complex, NW Spain)." Tectonophysics 401(3-4): 198-216.

The Concepenido eclogites are part of an ordered rock sequence in the upper tectonic unit of the Cabo Ortegal Complex (NW Spain). They form a continuous and about 200 m thick layer separating other mafic rocks from quartzo-feldspathic gneisses. The whole sequence has been deformed and metamorphosed at high pressure and high temperature during the development of an early Paleozoic subduction zone. In this study, microfabrics of these eclogites are quantitatively analysed, in particular crystallographic preferred orientations (CPO) in omphacite and garnet measured by electron back-scatter diffraction (EBSD). From field observations and from detailed microstructural analysis we estimate that the high pressure deformation, which produced the crystallographic and shape fabrics in omphacite, has occurred under a strain regime close to bulk coaxial flattening. Both omphacite lineations and omphacite c[001] concentrations scatter in geographical coordinates and do not show a single preferred orientation that would indicate a predominant direction of extension. We suggest that the high pressure and high temperature environment during deformation, the coaxial nature of strain and the significant thinning of the layer and rock sequence may relate to flattening deformation of a subducting slab with extension slightly preferred in a down-dip direction.




155.    Llorca, F. and G. Roy (2003). Metallurgical investigation of dynamic damage in tantalum. 13th APS Topical Conference on Shock Compression on Shock Compression of Condensed Matter, Portland, OR, USA, Bulletin of the American Physical Society.

In this paper, we investigate dynamic damage in tantalum. A wide range of shock pressure and pulse duration loadings is investigated. The aim of this work is to bring physical statements for the evaluation of multiscale damage models. From an experimental point of view, classical plates impact tests are performed for the generation of damage and fracture into tantalum. The recovery of shocked samples allows to make a complete investigation of the development of damage mechanisms. The use of various apparatus for the material investigations (optical micrography, EBSD, BEM, interferometric systems) gives us the opportunity to understand and quantify the evolution of the microstructure during the dynamic loading. We discuss the three main stages of damage and fracture (nucleation, growth and coalescence), giving at each time a physical understanding of the mechanism (intergranular germination, influence of micro inertia) and some quantified data (porosity, shape factors, inter voids distances). The variation of these observations and data within the shock pressure range is discussed and some specific aspects are focused.




156.    Lloyd, G. E. (2000). "Grain boundary contact effects during faulting of quartzite - An SEM/EBSD analysis." Journal of Structural Geology 22(11-12): 1675-1693.

During low-temperature faulting of Cambrian quartzite (Assynt, NW Scotland), stress concentrations develop at grain contacts either at the onset of deformation, prior to the establishment of a through-going fault plane, or within the damage zone remote from the main displacement segment. Such concentrations contribute to the development of intragranular microfractures, cataclastic microstructures and fault rocks. This contribution considers the progressive deformation sequence that precedes microfracturing and cataclasis. The complexity of this deformation is revealed by scanning electron microscope (SEM) electron backscattered diffraction (EBSD). Dauphiné twinning is a widespread feature associated with grain contact stress concentration and forms distinctive EBSD microstructures. Automatic SEM/EBSD analysis reveals that whilst initial indentation causes dauphiné twinning of many grains, continued indentation results in the formation of an arcuate array of subgrains via low temperature plasticity and/or microcracking, which overprint the dauphiné twins. These observations are consistent with transmission electron microscopic analysis of quartz crystals used for microhardness indentation tests, which reveal that indentation causes an intensely deformed region to develop, comprising a high density of microfractures and a submicron scale ‘blocky’ microstructure that accommodates any ‘plastic’ deformation. Deformation mechanisms and associated microstructures develop sequentially with progressive indentation and may provide sites of microfracture nucleation via low-temperature ductile fracture. The new microstructures assist diffusive mass transfer (DMT) processes by the formation of a cellular or subgrain array that represents a reduction of several orders of magnitude in apparent grain size and hence in diffusion path length. Concomitantly, associated microfracturing perturbs local thermodynamic equilibrium, leading to enhanced DMT, crack healing and cementation overgrowths. Together, these processes form the aseismic creep and sealing components of fault zone development.




157.    Lloyd, G. E., N. H. Schmidt, et al. (1991). "Crystallographic Textures." Mineralogical Magazine 55(380): 331-345.




158.    Loloee, R., S. Urazhdin, et al. (2004). On magnetic anisotropy of epitaxial Permalloy (111) films sputter deposited on epitaxial Nb(110). March Meeting of the American Physical Society, Montreal. Quebec, American Physical Society.

Epitaxial Permalloy (Py) thin films sputter deposited on epitaxial Nb with and without a buffer Cu layer have been investigated. Electron backscatter diffraction (EBSD) patterns were used to characterize the structural properties including the relative crystallographic orientation of the sputter deposited Nb, Cu, and Py films with respect to the substrate and each other. Rotational magnetization measurements were used to study the magnetic anisotropy of the films. A phenomenological model taking into account uniaxial anisotropy agrees well with the data, and provides a simple method for determinating the anisotropy strength. The effect of the epitaxial Nb buffer layer on the magnetic properties of the epitaxial Py film is discussed.




159.    Loloee, R., W. P. Pratt, et al. (2001). "Crystallographic Characterization of Sputter-Deposited Epitaxial Nb-Cu-Co and Nb-Cu-Permalloy Multilayers Using Electron Backscatter Diffraction Patterns." Philosophical Magazine A 81(2): 261-273.




160.    Long, M. D., X. Xiao, et al. (2006). "Lattice preferred orientation in deformed polycrystalline (Mg,Fe)O and implications for seismic anisotropy in D″." Physics of the Earth and Planetary Interiors 156(1-2): 75-88.

Magnesiowüstite [(Mg,Fe)O] is an important constituent of the lower mantle, probably occupying about 20–25% of its volume. Laboratory and theoretical studies have shown this mineral to be highly elastically anisotropic at lower mantle pressures and temperatures. Thus, strain-induced formation of lattice preferred orientation (LPO) in magnesiowüstite is a candidate mechanism for the origin of anisotropic structure in D″. Although observations of seismic anisotropy within D″ are robust, both the occurrence and the style of that anisotropy are spatially variable. Two hypotheses have been offered to explain the observations of D″ anisotropy: LPO of intrinsically anisotropic minerals, or shape preferred orientation (SPO), perhaps in the form of horizontal layering or oriented inclusions. To investigate the first hypothesis, we performed confined simple shear deformation experiments in the dislocation creep regime using a gas-medium deformation apparatus over a range of compositions: the MgO and FeO endmembers and three intermediate compositions. Samples were deformed at 1273–1473 K, at a confining pressure of 300 MPa, to large shear strains (γ = 3.5–4.5) using deformation pistons cut at 45°. After deformation, the LPO was measured by electron backscatter diffraction (EBSD). The LPO produced varied for differing compositions, indicating the activity on individual slip systems and/or the nature of grain boundary migration in (Mg,Fe)O are affected by composition and/or homologous temperature. We predicted seismic anisotropy from the measured LPOs and theoretically determined single-crystal elastic constants. Anisotropic behavior predicted from LPO agrees well with observations of D″ anisotropy, so the LPO hypothesis appears to satisfy the seismological constraints. Our calculated anisotropy patterns suggest that if D″ anisotropy is due to LPO of (Mg,Fe)O, then azimuthal variations in anisotropy in the horizontal plane should be present. Such azimuthal variations are not generally predicted for SPO-type hypotheses, and this may provide a means for distinguishing the cause of D″ anisotropy.




161.    Long, M., R. Crooks, et al. (1999). "High-Cycle Fatigue Performance of Solution-Treated Metastable- β Titanium-Alloys." Acta Materialia 47(2): 661-669.

The e.ect of grain boundary misorientation on the high-cycle fatigue performance of solution-treated, metastable-b titanium alloys was investigated. Initial damage during cyclic deformation was associated with the formation of coarse, planar slip bands, these often propagating through several grains without obstruction or redirection when intersecting with a grain boundary. This ``continuous'' slip through several grains was associated with the presence of a significant number of ``low-angle'' grain boundaries. Fatigue crack initiation was associated with crack initiation at intersecting planar slip bands at the free surface. The increase in operative slip length occasioned by the presence of low-angle grain boundaries lead to enhanced crack initiation and reduced lifetime. Fatigue crack propagation was characterized by step-like features formed through the interaction of the propagating crack and the coarse slip bands present in the plastic zone ahead of the crack tip. The direction of local fatigue crack propagation was also minimally affected when crossing low-angle grain boundaries. # 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.




162.    Longfei, L., Y. Wangyue, et al. (2003). "Dynamic recrystallization of ferrite during deformation at temperatures below Ac1 in a low carbon steel." Acta Metallurgica Sinica (China) 39(4): 419-425.

The hot deformation behavior of a Q235 class low carbon steel is investigated by plane strain compression tests on a Gleeble-2000 hot simulation test machine in the deformation temperature range of 700 to 550 degrees C, i.e. ferrite phase range, with the strain rate range of 1*101 to 5*10-4s-1, and the deformation microstructure evolution is investigated by means of SEM, TEM and EBSD The results indicate that under the present deformation conditions, dynamic recrystallization of ferrite, leading to grain refinement, is of continuous type at high hot deformation parameter Z values and discontinuous type at opposite conditions. The pearlites in this steel promote the progress of dynamic recrystallization. And the increase of parameter Z is of benefit to ferrite grain refinement that can lead to the formation of ultra-fine microstructures with average grain size of about 2 mu m.




163.    Longfei, L., Y. Wangyue, et al. (2006). "Dynamic recrystallization of ferrite in a low-carbon steel." Metallurgical and Materials Transactions A 37(3): 609-619.

Plane strain compression tests were performed on a low-carbon steel from 550°C to 700°C (ferrite-phase range) at strain rates of 10 to 5 x 10-4s-1, and the deformation microstructure evolution was investigated by means of scanning electron microscopy, transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD). The results indicate that under the present deformation conditions, dynamic recrystallization of ferrite can occur in the low-carbon steel and lead to grain refinement. With increasing Zener-Hollomon parameter Z, the mechanism of this process changes from discontinuous dynamic recrystallization to continuous dynamic recrystallization; the turning point is approximately at Z = 1 x 1016s-1. The increase of parameter Z leads to the decrease of recrystallized grain size of ferrite under steady state of deformation, and can lead to the formation of ultrafine microstructures with average grain size of about 2 µm.




164.    Lorimer, G. W., L. W. F. Mackenzie, et al. (2004). The recrystallization behavior of AZ31 and WE43. International Conference on Magnesium – Science, Technology and Applications, Beijing, China, TransTech Publications.

The deformation and recrystallization behavior of two magnesium alloys, AZ31 and WE43, have been investigated. The cast alloys were heat treated to produce various distributions of second phase particles and deformed in a channel die at a strain rate of 10-4 s-1 at temperatures between 523 and 673 K. The alloys were subsequently annealed at temperatures between 708 and 798 K. The AZ31 and WE43 were extruded at 555 and 633 K, respectively. The microstructures were compared to those developed during channel die deformation. The tensile and compressive strengths and the texture of the alloys were determined in the as-extruded and recrystallised conditions. Optical microscopy and electron backscattered diffraction (EBSD) were used to characterize the microstructures of the alloys. The EBSD technique was used to determine the texture of the deformed and annealed samples.




165.    Lou, J., S. Allameh, et al. (2003). "An investigation of the effects of thickness on mechanical properties of LIGA nickel MEMS structures." Journal of Materials Science 38: 4129-4135.

This paper examines the effects of thickness on the mechanical properties of LIGA Ni MEMS structures plated from sulfamate baths. The as-plated LIGA Ni specimens of different thickness (50 μm, 100 μm and 200 μm) were utilized in the microtensile experiments. Optical microscopy, orientation imaging microscopy and scanning electron microscopy were used to characterize the microstructure of the LIGA Ni specimens. Fracture Modes obtained from specimens with different thickness were revealed by scanning electron microscopy. The effects of specimen thickness are then discussed within the context of strain gradient plasticity theories.




166.    Louisweber, M. S., V. P. Dravid, et al. (1996). "Transport-Properties of an Engineered (001)-Tilt Series in Bulk YBz2Cu3O7-X Bicrystals." Physical Review B 54(22): 16238-16245.




167.    Lu, H., P. Sivaprasad, et al. (2003). "Treatment of misorientation data to determine the fraction of recrystallized grains in a partially recrystallized metal." Materials Characterization 51: 293-300.

A method has been developed to differentiate recrystallized from unrecrystallized grains in partially annealed samples based on the point-to-point misorientation within the grains. Recrystallized grains exhibit a low average point-to-point misorientation whereas the contrary is the case for deformed grains. The analysis for recrystallized fraction was calibrated based on this distinguishing feature, and it was found that the average point-to-point misorientation within a grain in a fully recrystallized sample was less than 0.7°. Based on this calibration, partially recrystallized samples were analysed for their degree of recrystallization, and the technique was validated using microhardness measurements. The analysis of the misorientation data was in excellent agreement with the hardness data. There are three factors which distinguish the current method in comparison to the earlier work: a fixed limit is maintained on the minimum number of pixels which may constitute a grain; pattern quality is not considered; and the recrystallization criterion is calibrated to the experimental data. Nevertheless, in the early stages of annealing, where recovery is likely to have the most influence on the drop in hardness, the analysis of electron backscattered diffraction (EBSD) data underpredicts the recrystallized fraction. The analysis was also conducted on a cold-rolled, nonannealed sample, and from this, the error of the technique is estimated to be a maximum of 0.06 recrystallized volume fraction.




168.    Lu, P., Y. Zhou, et al. (2006). "Single-phase β-FeSi2 thin films prepared on Si wafer by femtosecond laser ablation and its photoluminescence at room temperature." Physics Letters 350: 293-296.

Single-phase β-FeSi2 thin films were prepared on Si(100) and Si(111) wafers by using femtosecond laser deposition with a FeSi2 alloy target for the first time. X-ray diffraction (XRD), field scanning electron microscopy (FSEM), scanning probe microscopy (SPM), electron backscattered diffraction pattern (EBSD), and Fourier-transform Raman infrared spectroscopy (FTRIS) were used to characterize the structure, composition, and properties of the β-FeSi2/Si films. The orientation of β-FeSi2 grains was found to depend on the orientation of the Si substrates, and photoluminescence at wavelength of 1.53 μm was observed from the single-phase β-FeSi2/Si thin film at room temperature (20°C).




169.    Ludwig, W., J.-Y. Buffiere, et al. (2003). "Study of the interaction of a short fatigue crack with grain boundaries in a cast Al alloy using X-ray microtomography." Acta Materialia 51(3): 585-598.

Synchrotron Radiation X-ray microtomography is used to visualize and analyze simultaneously the three-dimensional shape of crystallographic grains containing a short fatigue crack in a cast Al alloy AS7G03. The visualization of the grains is based on the decoration of Al grain boundaries by liquid Ga which serves as a selective contrast agent. The intricate three-dimensional shape of the fatigue crack, as well as the crack stops observed on the sample surface, are correlated to the grain structure of the material. Complementary measurements of the grain orientation on the sample surface by electron backscattering diffraction (EBSD) allow us to discuss and interpret the observations in terms of possible crack propagation mechanisms.




170.    Lukas, P., L. Kunz, et al. (2005). "Fatigue notch sensitivity of ultrafine-grained copper." Materials Science and Engineering A 391(1-2): 337-341.

Fatigue notch sensitivity of ultrafine-grained (UFG) copper of purity 99.9% produced by equal channel angular pressing was determined on cylindrical specimens with circumferential notches of different radii and compared with the notch sensitivity of conventional copper. Notch sensitivity of UFG copper is higher than that of its conventional counterpart. Electron back scattering diffraction technique showed that the UFG copper of purity 99.9% is not prone to grain coarsening during cycling. The grain structure within plastic zone around the cracks was found to differ substantially from that outside the plastic zone: the grains were markedly elongated, but their size was preserved.




171.    Luo, J. F., Y. Ji, et al. (2006). "EBSD measurements of elastic strain fields in a GaN/sapphire structure." Microelectronics Reliability 46(1): 178-182.

An elastic strain field of the heteroepitaxial GaN layer grown on the sapphire substrate, containing a buffer interlayer, was measured using the electron backscatter diffraction (EBSD). Pattern qualities, Hough transforms and small misorientations of Kikuchi bands on EBSD patterns, as strain sensitive parameters and referred to diffraction intensities, were performed to evaluate the elastically distorted region within the sample. The elastic strain gradient parallel to the growth direction of GaN epilayers was mapped and a strain range from 100nm to 200nm was detected.




172.    Luo, J., Y. Ji, et al. (2005). "EBSD analysis of the melting joints of Ti alloys." Chinese Journal of Stereology and Image Analysis 10(4): 241-243.

Electron backscatter diffraction (EBSD) technique was performed to measure and analyze the characteristics of the crystallographic orientation, the grain structure and the grain boundary in the melting pool and the hot affect zone (HAZ) of the melting joints of Ti-Al-Nb alloy fabricated by the CO2 laser beam welding technology. Furthermore, the image quality parameters (IQ) of the EBSD Kikuchi bands confirm that the residual stress in the weld joints is released during annealing.




173.    Luzin, V., S. Banovic, et al. (2005). Measurement and Calculation of Elastic Properties In Low Carbon Steel Sheet. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.

Low carbon steel (usually in sheet form) has found a wide range of applications in industry due to its high formability. The inner and outer panels of a car body are good examples of such an implementation. While low carbon steel has been used in this application for many decades, a reliable predictive capability of the forming process and “springback” has still not been achieved. NIST has been involved in addressing this and other formability problems for several years. In this paper, texture produced by the in-plane straining and its relationship to springback is reported.

Low carbon steel sheet was examined in the as-received condition and after balanced biaxial straining to 25%. This was performed using the Marciniak in-plane stretching test. Both experimental measurements and numerical calculations have been utilized to evaluate anisotropy and evolution of the elastic properties during forming.

We employ several techniques for elastic property measurements (dynamic mechanical analysis, static four point bending, mechanical resonance frequency measurements), and several calculation schemes (orientation distribution function averaging, finite element analysis) which are based on texture measurements (neutron diffraction, electron back scattering diffraction). The following objectives are pursued: a) To test a range of different experimental techniques for elastic property measurements in sheet metals; b) To validate numerical calculation methods of the elastic properties by experiments; c) To evaluate elastic property changes (and texture development) during biaxial straining. On the basis of the investigation, recommendations are made for the evaluation of elastic properties in textured sheet metal.




173 records found

 

 

  
Overview Press Releases and Trade Shows Services & Support Literature Our Products Contact Sales Our Locations Related Web Sites Privacy Policy Trademarks Map