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64 records found
1.
Na, Y. S., M. H. Lee, et al. (2003). "EBSD Analysis of Grain Structure of Hot-Compressed Ni-Based Superalloy 718." Journal of the Korean Institute of Metals and Materials 41(3): 196-201.
In order to characterize the dynamic change of microstructures in commercially-available superalloy 718, a series of compression tests were conducted by varying test temperature and strain rate. Orientation relationship and the misorientations between recrystallized grains as well as unrecrystallized grains were thoroughly investigated with EBSD technique. The dynamically-recrystallized grain size was similar regardless of the compression test condition except for the sample tested at 1066 deg C-0.005/sec condition, where the dynamically-recrystallized grain size was as large as 20 mu m in average diameter. In case of the sample tested at 1066 deg C, flow stress drops caused by the strain softening were almost same at the strain rates of 0.5/sec and 0.005/sec in spite of the different fraction of dynamic recrystallization. It was concluded from the observation of the misorientation angle distribution that it was due to the active dynamic recovery in the unrecrystallized large grains at high temperature. It was also suggested from the variations of CSL boundary distribution that the characteristic redistribution of the dynamically-recrystallized grain boundary might be taken place during the compression at high temperature and low strain rate
2.
Na, Y.-S., J.-T. Yeom, et al. (2006). "Electron Backscatter Diffraction Analysis of Dynamically Recrystallized Grain Structures in a Ni-Cr-Fe Base Alloy." Metallurgical and Materials Transactions A 37(1): 41-48.
Dynamic variations in grain structures and grain boundary characteristics of NiCrFe-based alloy 718 during hot uniaxial compression as well as stress relaxation after the compression were investigated in this article. An electron backscatter diffraction (EBSD) technique was used for the specimens that were compressed at temperatures of 1010°C and 1066 °C and strain rates of 0.5 and 0.005 s–1, up to a strain of 0.7. Stress relaxation was observed by keeping the upper die in position at the test temperatures as soon as the compression was completed. The variations in the CSL boundary distribution and in the misorientation angle distribution during compression and stress relaxation were thoroughly analyzed to characterize the dynamically recrystallized grain (DRX) boundaries. During deformation at a high strain rate of 0.5 s–1, dynamically recrystallized grains were formed by progressive subgrain rotation. Active dynamic recovery (DRV) at 1066°C was inferred from the similar degree of strain softening in spite of the different fraction of dynamic recrystallization, which is supported by the high frequency of low misorientation angle boundaries. Stress relaxation was caused by a coalescence of subgrains having very small misorientation angles. Directional grain growth and a redistribution of the grain boundary character caused by the grain rotation occur during the stress relaxation, resulting in reduced total boundary energy.
3.
Naess, S. E. (1991). "Development of Annealing Textures in the Aluminum-Alloys Aa3005 and Aa5050." Zeitschrift fur Metallkunde 82(6): 448-458.
4.
Nagashio, K. and K. Kuribayashi (2005). "Growth mechanism of twin-related and twin-free facet Si dendrites." Acta Materialia 53(10): 3021-3029.
The various types of facet Si dendrites observed on splat-quenched surfaces were analyzed in order to understand why the growth direction and morphology of the facet Si dendrites change with increasing undercooling. The growth directions of typical facet dendrites were determined to be (211), (110) and (100) using an electron backscatter pattern apparatus. It was found that both the (211) and (110) dendrites with twins were bounded by atomically smooth {111} planes. Therefore, their growth is governed by the incorporation of atoms at re-entrant corners formed by twins. The (100) dendrites with fourfold symmetry have no twins and are commonly observed at high undercoolings. Moreover, two kinds of (100) dendrites with different secondary arm directions (100) and (110) were clarified for the first time. The dendrite tip shape and facet planes, as determined using an atomic force microscope, suggest that the (100) dendrites are bounded by atomically rough {110} and {100} planes. That is, facet Si dendrites vary in their growth direction and morphology with increasing undercooling because the dendrites select atomically rough interfaces in order to promote the incorporation of atoms at high undercoolings.
5.
Nagashio, K. and K. Kuribayashi (2006). "Experimental verification of ribbon formation process in chill-block melt spinning." Acta Materialia 54(9): 2353-2360.
The rapid solidification process in melt spinning has been empirically deduced from the relationship between the resultant phases/microstructure and the wheel speed, because the melt-substrate interface is difficult to observe directly. The controversy over whether the ribbon solidifies in or outside the melt puddle (thermal or momentum transport control) still remains unresolved. We report the first in situ observation of the melt-substrate interface. The silicon melt was ejected onto a silicon wafer rotated “transversely” by a motor in a chamber. The silicon wafer, which is transparent for wavelengths >1.1 μm, can be used as the chill substrate to simulate rapid solidification on a copper substrate, since the thermal conductivity of silicon is of the same order of magnitude as that of copper. Successive images captured through the silicon wafer by high-speed infrared imaging revealed that the ribbon solidified just at the underside of the melt puddle. It was demonstrated that ribbon formation is controlled by thermal transport.
6.
Nagashio, K., H. Murata, et al. (2004). "Spreading and solidification behavior of molten Si droplets impinging on substrates." Acta Materialia 52(18): 5295-5301.
This paper focuses on an effect of initial undercoolings on the spreading and solidification behavior of Si dropped on a silicon wafer, which was directly observed through it by the infrared imaging system. For an overheated droplet, the melt spreading occurred first and solidified later. The final splat shape was a typical disc. On the other hand, for a droplet with large initial undercooling, the solidification took place at the faster rate than the melt spreading, which resulted in a spherical shape of final splat. It is indicated that the final shape is considerably affected by the initial undercooling in the measurable-scale experiment with large droplets (mm size) and low impingement rates (m/s order). Moreover, equiaxed grains were found throughout the quenched surface by an electron backscatter pattern analysis. That is, the microstructure formation was nucleation-controlled since the growth parallel to the substrate was suppressed by the time-dependent contact of melt-substrate governed by the melt deformation.
7.
Nagashio, K., H. Okamoto, et al. (2005). "Fragmentation of Faceted Dendrite in Solidification of Undercooled B-Doped Si Melts." Metallurgical and Materials Transactions A 36A(12): 3407-3413.
The fragmentation of the faceted dendrite of B-doped Si solidified from the undercooled melt was investigated using an electromagnetic levitator. The <110> dendrites, which grew at ΔT < ~100 K, never fragmented because they were composed of {111} planes with the lowest interface energy. On the other hand, the <100> dendrites, which grew at ΔT > ~100 K, showing fourfold axial symmetry, broke up into small pieces at undercoolings of more than 200 K. It was suggested that the capillary force acts on the interface with a relatively high energy to break up the dendrite into small pieces, since the <100> dendrites are composed of {110} and {100} planes with interface energies larger than that of the {111} plane. Moreover, striations of concentric circles formed by the segregation of B revealed that the remaining melt solidifies from the surface toward the center to engulf the fragmented dendrites. This solidification process seems different from those of typical metallic materials, in which the fragmented dendrites are randomly distributed throughout the sample and the remaining liquid solidifies from the fragmented dendrites. This solidification characteristic was discussed in relation to the influence of electromagnetic force on the microstructure of Si.
8.
Nakai, M., H. Kaiden, et al. (2005). "Eutectic Al2O3/Y3Al5O12 fibers modified by the substitution of Sc2O3, Fe2O3 or Cr2O3." Journal of the European Ceramic Society 25(8): 1405-1410.
A variety of corundum/garnet eutectic fiber samples were produced by the micro-pulling-down (mu -PD) method in an Ar atmosphere and the substitution of Cr2O3, Fe2O3 or Sc2O3 for Al2O3 in the eutectic fiber sample 0.81Al2O30.19Y2O3 was studied by a scanning electron microscope (SEM) and electron backscattering (EBSP) together with the X-ray diffraction (XRD). Although the chemical substitution resulted in the formation of a colony structure consisting of a fine ordered "Chinese-script" structure of corundum and garnet surrounded by a thick boundary region, a fundamental crystallographic relationship <001> corundum//<112> garnet was found to be perpendicular to the solidification direction was readily observed. Cr2O3 is distributed in corundum and garnet structures, Sc2O3, however, preferred the garnet structure. The EDX and XRD analyses showed that the presumably reduced FeO contributes to the formation of hercynite FeAl2O4.
9.
Nakamachi, E., Y. CHEN, et al. (2004). Development of crystallographic homogenization finite element method to study crystal texture effects on sheet formability. Materials Processing and Design. Modeling, Simulation and Applications. NUMIFORM 2004. Proceedings of the 8th International Conference on Numerical Methods in Industrial Forming Processes, Columbus, Ohio, USA, AIP.
A "semi-implicit" elastic/crystalline viscoplastic finite element analysis (FEA) code based on a "crystallographic homogenization" theory for the multi-scale analysis is developed, by introducing SEM-EBSD measured crystal texture. The homogenization algorithm is introduced to calculate macro-continuum plastic deformations and material properties by considering a micro-structural in-homogeneity, which is characterized by the crystal texture and the initial and deformation induced hardening evolutions. Its micro-structure is defined as the unit cell, which satisfy the periodicity condition, where both compatibility and equilibrium are satisfied. The conventional rate-dependent type crystal plasticity constitutive equation is employed in a micro-structure modeling. In the homogenization procedure, the asymptotic series expansion is introduced to define the displacement, which can be decomposed into two parts: the homogenized deformation defined by using the macro-continuum displacement and the perturbed one, defined only in the micro-structure. This "two-scale" analysis code enables to carry out transition from a representative micro-structure to the macro-continuum. This consistency model satisfies both the compatibility and the equilibrium in the micro-structure. This homogenization FE code is applied to study texture evolution induced by the plastic deformation, assess the formability of sheet metal, which has a ferrite phase, and confirm the availability through comparison with EBSD-SEM observation results.
10.
Nakamichi, E. (2004). Development of triple scale finite element analyses based on crystallographic homogenization methods. Materials Processing and Design: Modeling, Simulation and Application Proceedings of NUMIFORM, Columbus, Ohio, USA, AIP.
Crystallographic homogenization procedure is implemented in the piezoelectric and elastic-crystalline plastic finite element (FE) code to assess its macro-continuum properties of piezoelectric ceramics and BCC and FCC sheet metals. Triple scale hierarchical structure consists of an atom cluster, a crystal aggregation and a macro-continuum. In this paper, we focus to discuss a triple scale numerical analysis for piezoelectric material, and apply to assess a macro-continuum material property. At first, we calculate material properties of perovskite crystal of piezoelectric material, XYO3 (such as BaTiO3 and PbTiO3) by employing ab-initio molecular analysis code CASTEP. Next, measured results of SEM and EBSD observations of crystal orientation distributions, shapes and boundaries of a real material (BaTiO3) are employed to define an inhomogeneity of crystal aggregation, which corresponds to a unit cell of micro-structure, and satisfies the periodicity condition. This procedure is featured as a first scaling up from the molecular to the crystal aggregation. Finally, the conventional homogenization procedure is implemented in FE code to evaluate a macro-continuum property. This final procedure is featured as a second scaling up from the crystal aggregation (unit cell) to macro-continuum. This triple scale analysis is applied to design piezoelectric ceramic and finds an optimum crystal orientation distribution, in which a macroscopic piezoelectric constant d33 has a maximum value.
11.
Nakamura, S. and H. Homma (2004). Micro-Scale OIM Study on the Recrystallization Process of Cold Rolled α-Fiber Single Crystal. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
Recrystallization of cold rolled {211}<011> single crystal of 3.5%Si-Fe were investigated by electron back-scattered pattern (EBSP) technique in order to clarify the formation of {h,1,1}<1/h, 1, 2> fiber in recrystallization texture of steel with high cold rolling reduction. In the cold rolled sample, there exist shear-band like substructures characterized by the orientation fluctuation with single <011> axis whereas their orientations are almost kept to the original orientation {211}<011> which belongs to α-fiber (RD//<110> fiber). In the recovery stage, the orientation fluctuations are enhanced and include fluctuations with another <011> axis. That is the fluctuations in the recovery stage are not characterized by rotation relationship with single <011> axis. The recrystallization texture includes {100}<012> and {411}<148> as major orientations in {h,1,1}<1/h, 1, 2> fiber. Furthermore, there exists clear orientation relationship characterized by multiple rotations with <011> axes between the recrystallization orientations and the original one. Actually, orientations characterized by rotational relationships with <211> (=[110] + [101]) axis and <111> (=[110]+[101]+[011]) were observed. These results suggest that recrystallization from a-fiber is occurred as a result of the final enhanced stage of the fluctuations characterized
12.
Nakamura, S., Y. Ushigami, et al. (2002). Coincidence Grain Boundary and Selective Growth of Goss Grain in Fe-3%Si Alloy. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.
Effect of coincidence grain boundary on selective growth of secondary recrystallized Goss grain has been investigated to direct crystallographic measurement of Goss-primary matrix interface using electron backscattered diffraction (EBSD). The primary recrystallized specimens were partially secondary recrystallized by temperature gradient annealing to enhance the selectivity of grain growth. In this examination the two orientation relationships were measured: (1) the orientation relationship between the Goss grain and the neighboring primary matrix grains along the periphery of the Goss grains and (2) the orientation relationship between the Goss grain and the primary matrix grains which are not adjoining the Goss grain. It was found that the frequency of low-angle boundaries (S1 CSL boundaries) between the Goss grain and the neighboring primary matrix grains are higher than the expected values of random migration and that of near-S9 CSL boundaries (twice of misorientation due to the Brandon's criterion) are lower. These features suggest that low-angle boundaries are immobile and near-S9 CSL boundaries are mobile during the selective growth of Goss grain in the secondary recrystallization. The mechanism of selective growth of secondary recrystallized Goss grain can be explained due to the preferential migration of near-S9 CSL boundaries in the presence of inhibitor.
13.
Nakamura, T., S. Ochiai, et al. (2005). "Relation between Cracking of Intermetallic Coating Layer of Galvannealed Steel Sheet and Grain Boundary of Substrate Steel." Tetsu-to-Hagane (Journal of the Iron and Steel Institute of Japan) 91(3): 342-348.
Multiple cracking behavior and its relation to the grain boundary of the substrate steel were investigated. The crack spacing and its distribution of the specimens strained to prescribed strains were observed with a scanning electron microscope. The crystallographic orientation of the substrate grains was estimated from the electron back scattering pattern. The images of the cracks of the coating layer and grain boundaries of the substrate steel were combined together with image processing software to know whether the cracking of coating layer initiates above the substrate grain boundaries or not. The main results are summarized as follows. (I) The cracking of the coating layer initiates in the regions just above the substrate grain boundaries. (2) The cracks that initiate above the substrate grain boundaries propagate transversely; namely they propagate into the region, below which no substrate grain boundary exists. (3) It was suggested the cracking of the coating layer initiates above the small angle grain boundaries or above the grain boundaries intact to the grains with large Schmid factors. (4) In the multiple cracking process of the coating layer, the similarity of the crack spacing distribution to the grain boundary spacing distribution is kept.
14.
Nakashima, H., D. Terada, et al. (2001). "EBSP analysis of Modified 9Cr-1Mo Martensitic steel." ISIJ International 41: S97-100.
In order to clarify the structure change of 9Cr-1Mo tempered martensitic steel during the high temperature creep, the structures deformed were observed by SEM-OIM and TEM method. It was found that initial bolock and packet structures were well equi-axed. These structures were very stable during creep, but just before rupture changed to elongate grain. From an analysis of the grain boundary, Σ3 (rotation angle 70.5°), near Σ11 (rotation angle 50.5°) and small angle (rotation angle 10°) boundaries existed in the martensite. This result agrees with the result predicted with K-S orientation relationship. It was also found that the density of Σ3 boundary or near Σ11 boundary decreased during high temperature creep. But, it was found that the density of Σ3 boundary decreased, and that of near Σ11 and small angle boundaries increased during the high temperature deformation. In initial structure, relative frequency of <110> common axis (Block boundary) is largest to compare with other axes. But, just before the rupture, relative frequency of <110> (Block boundary) suddenly decreased and <123> and <233> (not Block or Packet boundaries increased
15.
Narutani, T. and J. Takamura (1991). "Grain-Size Strengthening in Terms of Dislocation Density Measured by Resistivity." Acta Metallurgica et Materialia 39(8): 2037-2049.
16.
Nast, R., B. Obst, et al. (2004). "BiTEP (biaxially textured electroplating): a novel route for making improved coated conductors, based on a well established technique." Superconductor Science and Technology 17(4): 710-716.
We present a new technique for the deposition of Ni on cube textured Ni alloy substrates. It is superior to the commonly used PVD and CVD coating methods and easy to scale up from the laboratory to an industrial long length process. The new route, called `BiTEP' (biaxially textured electroplating), where biaxially textured Ni alloy substrates are electrolytically plated with Ni, is shown to lead to an outstanding transfer of the texture from the substrate to the pure Ni layer. Several platings from 130 nm to 1.5 mu m thickness were made on Ni96W4, Ni87Cr6.5W6.5 and Ni90Cr10 substrates, applying different current densities during electroplating, from 0.2 to 2 A dm-2. All investigated samples showed epitaxy between the substrates and the Ni film, independent of the layer thickness, the current density used for electroplating, and the substrate material. In Ni-W substrate tapes a sharp cube recrystallization texture with FWHM (111) of <5 degrees was achieved, leading to a current density of 1.35 MA cm-2 (77 K, self-field) in YBCO. Furthermore, commercially available constantan (Ni 44.4 wt%, Cu 54.19 wt%, the rest: Mn, Fe) from our partner ThyssenKrupp VDM was investigated.
17.
Naumovic, D. (2004). "Structure and electronic structure of quasicrystal and approximant surfaces: a photoemission study." Progress in Surface Science 75(3-8): 205-225.
The structure and electronic structure of different high-symmetry surfaces of either quasicrystalline or approximant Al–Pd–Mn were studied by means of photoemission-based techniques such as X-ray photoelectron diffraction (XPD) and ultraviolet photoelectron spectroscopy. We find that the twofold (2f), 3f and 5f surfaces of icosahedral Al–Pd–Mn exhibit all the symmetry elements of the icosahedral non-crystallographic group. These XPD experiments can be modeled by single-scattering cluster calculations. The bulk-terminated icosahedral or approximant surfaces are recovered after ion sputtering followed by annealing at T˜500–600 °C. A wealth of ordered surface phases (with different compositions) are found after sputtering and depending on the annealing temperature as, for example, a crystalline bcc multitwinned phase (for T<400 °C) or a stable decagonal quasicrystalline surface (for T>650 °C). The icosahedral surfaces are characterised by a lowering of the density of states close to the Fermi edge, compatible with the opening of a pseudogap, as expected for a quasicrystal. The crystalline overlayers are characterised by a sharp Fermi edge, while the approximant and decagonal quasicrystalline surfaces also have a lowered density of states.
18.
Naumovic, D., P. Aebi, et al. (2001). "Formation of a Stable Decagonal Quasicrystalline Al-Pd-Mn Surface Layer." Physical Review Letters 87(19).
We report the in situ formation of an ordered equilibrium decagonal Al-Pd-Mn quasicrystal overlayer on the fivefold symmetric surface of an icosahedral Al-Pd-Mn monograin. The decagonal structure of the epilayer is evidenced by x-ray photoelectron diffraction, low-energy electron diffraction, and electron backscatter diffraction. This overlayer is also characterized by a reduced density of states near the Fermi edge as expected for quasicrystals. This is the first time that a millimeter-size surface of the stable decagonal Al-Pd-Mn is obtained, studied, and compared to its icosahedral counterpart.
19.
Nave, M. D. and M. R. Barnett (2002). Recrystallization Textures in Coarse Grained Low Carbon and Interstitial Free Steels. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.
The microstructures and textures of coarse grained cold rolled, partially recrystallized and fully recrystallized low carbon and interstitial free steel were examined by optical microscopy, scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD)The recrystallization textures of the two grades are markedly different, with the low carbon steel having a predominantly goss {110}<001> texture and the interstitial free steel having a <111>//ND texture with a strong {111}<112> component. One possible explanation for the texture difference is that less severe localization of flow during deformation of interstitial free steels causes less Goss nuclei to be generated. While some support for this view is provided by the results presented in this paper, the results suggest that another mechanism may be at least partially responsible. Examination of micro shear bands on the surface of pre-polished samples showed that a higher proportion of micro shear bands remained active at high rolling reductions in the low carbon steel, compared with the interstitial free grade. Regions of Goss orientation within bands that have ceased to operate rotate to near-{111}<112> orientations with further deformation. Consequently, the recrystallization texture of coarse grained interstitial free steels can be rationalized by a reduction in the availability of Goss nuclei and an increase in the availability of {111}<112> nuclei due to a "Goss to {111}<112>" rotation within micro shear bands that have ceased to operate.
20.
Nave, M. D. and M. R. Barnett (2004). "Microstructures and textures of pure magnesium deformed in plane-strain compression." Scripta Materialia 51(9): 881-885.
Microstructures of textured polycrystalline Mg samples compressed parallel and perpendicular to the predominant c-axis direction in a channel die are characterized using EBSD. Anomalous peaks in the misorientation angle distribution of the latter sample result from twinning on two different { 1 0 1 2 } planes within individual grains.
21.
Nave, M. D. and M. R. Barnett (2004). "Texture change near grain boundaries and triple points in cold-rolled interstitial-free steel." Materials Science and Engineering 386(1-2): 244-253.
Although regions near grain boundaries and triple points are important sources of nuclei during the recrystallization of cold-rolled interstitial-free steels, previous characterizations of orientational change in these regions have examined a relatively small number of grains. This work employs electron backscatter diffraction (EBSD) to quantify, over a very large number of grains, differences in texture between regions near grain boundaries, near triple points and in the interiors of grains. Compared with the texture of the grain interiors, the textures of regions near grain boundaries and triple points are weaker and the maxima on the RD-fibre are closer to {0 0 1} <1 1 0>. The texture changes near grain boundaries and triple points are discussed in relation to textures produced by plasticity models as well as measured nucleation textures.
22.
Nave, M. D., J. J. L. Mulders, et al. (2005). "Twin Characterisation using 2D and 3D EBSD." Chinese Journal of Stereology and Image Analysis 10(4): 199-204.
Electron backscatter diffraction (EBSD) is a superior technique for twin characterisation due to its ability to provide highly detailed classification (by generation, system and variant) of a significant number of twins in a relatively short time. 2D EBSD is now widely used for twin characterisation and provides quite good estimates of twin volume fractions under many conditions. Nevertheless, its accuracy is limited by assumptions that have to be made due to the 2D nature of the technique. With 3D EBSD, two key assumptions are no longer required, as additional information can be derived from the 3D map. This paper compares the benefits and limitations of 2D and 3D EBSD for twin characterisation. 2D EBSD enables a larger number of twins to be mapped in a given space of time, giving bettter statistics. 3D EBSD provides more comprehensive twin characterisation and will be a valuable tool for validation of 2D stereological methods and microstructural models of twinning during deformation.
23.
Nave, M. D., K. Verbeken, et al. (2004). On the Production of Randomly-Oriented Recrystallization Nuclei for Selective Growth Experiments. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
The ideal starting condition for selective growth experiments is one having a layer of randomly-oriented nuclei adjacent to a matrix with negligible orientational variation but sufficient stored energy to promote growth. In practice, cutting or deformation processes are used in an attempt to approximate these ideal conditions, but the degree to which this is achieved has not been rigorously quantified. In this work, Fe-3wt%Si single crystals were cut or deformed using six different processes. The variation in texture with distance from the cut or deformed surface was measured using electron backscatter diffraction (EBSD) in a field emission gun scanning electron microscope (FEG-SEM) in order to assess the ability of each process to create conditions suitable for selective growth experiments. While grooving with a machine tool produced the best spread of orientations at the cut surface, the suitability of this process is diminished by the presence of a differently-textured deformed layer between the cut surface and the single crystal matrix. Grinding produced a less ideal distribution of orientations at the cut surface, but the presence of these orientations in a very thin layer adjacent to the matrix makes this process preferable for preparing crystals for selective growth experiments, provided the results are corrected for the deviation in the distribution of nuclei orientations from a random distribution.
24.
Necker, C. T., A. D. Rollett, et al. (1995). The development of cube and non-cube recrystallization textures. 16. Risoe international symposium on materials science: microstructural and crystallographic aspects of recrystallization, Roskilde, Denmark.
The development of recrystallization textures in cold rolled copper has been characterized using an electron backscatter pattern (EBSP) technique. Cube oriented grains exist in materials that have been annealed after a series of rolling strains, between 1.0 and 4.5 (von Mises strain). The strength and sharpness of these cube textures increases with increasing strain thus replacing the random texture produced by recrystallization of moderately deformed copper. The preferential formation of the cube, texture is attributed to the homogenization of stored energy gradients adjacent to randomly oriented nucleation sites. This process, coupled with the development of the microstructure adjacent to deformed cube sites, favors nucleation and growth of cube grains over randomly oriented grains.
25.
Necker, C. T., D. J. Alexander, et al. (2005). Equal Channel Extrusion Heterogeneities in Recrystallized Copper. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
Various processing routes have been studied to develop the most efficient route toward microstructure refinement and texture homogenization. Most studies have focused on the central shear zone in round or square cross-section rods. However, the utility or application of these materials is subject to conditions across the entire rod. This study begins to investigate the development of recrystallization textures and microstructures across copper ECAE processed via route Bc through 16 passes. Although the recrystallized condition appears to be reasonably homogeneous after 4 or 8 passes, additional passes lead to stronger, heterogeneous recrystallization textures and coarsened microstructures.
26.
Necker, C. T., R. D. Doherty, et al. (1996). Development of recrystallization texture and microstructure in cold rolled copper. ReX `96: International conference on recrystallization and related phenomena, Monterey, California, USA.
Oxygen free electronic copper, 99.995% purity, of two initial grain sizes, 50 µm and 100 µm, has been cold rolled to six strains of 1.0, 1.5, 2.0, 2.65, 3.5 and 4.5 (von Mises equivalents). The rolled materials were partially and fully recrystallized to study the development of recrystallization textures as a function of grain size, strain and fraction recrystallized. The initial textures were relatively random and the deformation textures show the classic β fiber development. As strain is increased both materials produce increasingly intense cube recrystallization textures, (100)<001>, as measured both by x-ray diffraction and the electron backscatter pattern (EBSP) techniques. The strong cube recrystallization textures are a product of a higher than random frequency of cube nucleation sites. An additional factor is that cube regions grow larger than non-cube regions. The explanation of the cube frequency advantage is based on the development of large stored energy differences between cube orientations and neighboring orientations due to recovery of cube sites. Of several possible explanations of the cube orientation size advantage, the most plausible one is solute entrapment. At the higher strains the boundaries of cube grains encounter the deformation texture S components, (123)<634>, changing the boundary character to one of 40°<111>. These boundaries are more resistant to solute accumulation than random high angle boundaries, allowing the boundaries to migrate with less of a solute drag effect than a random high angle boundary.
27.
Nekkanti, R. M., V. Seetharaman, et al. (2001). "Development of Nickel Alloy Substrates for Y-Ba-Cu-O Coated Conductor Applications." IEEE Transactions On Applied Superconductivity 11(1): 3321-3324.
28.
Nelson, T. W., B. Hunsaker, et al. (1999). Local Texture Characterization of Friction Stir Welds in 1100 Aluminum. First International Symposium on Friction Stir Welding, Thousand Oaks, CA.
29.
Neu, R. W. and D. R. Swalla (2005). Role of misorientation in assessing fretting damage. 2005 World Tribology Congress III, Washington, D.C., USA.
The primary focus of the current work is to develop quantifying measures that can describe the evolution of fretting damage at the microstructural scale in a dual phase Ti-6Al-4V as well as two single phase materials: commercially pure titanium (CP-Ti), which consists of pure alpha-phase titanium, and a near alpha Ti-5Al-2.5Sn. It is important to understand deformation behavior at the microstructural scale in heterogeneous materials because features at this scale, such as grain size, crystallographic orientation, and phase distribution, strongly influence crack development and are dimensionally of the same magnitude as the fretting damage volume. In Ti-6Al-4V, the size, distribution, and crystallographic orientation of the alpha-phase, which has an HCP crystalline structure, is particularly significant in fretting crack formation. Recent studies have linked an increase in average intra-grain misorientation (AMIS) measured using electron backscatter diffraction (EBSD) to increasing strain in medium to high stacking fault metals such as titanium, nickel, copper, and aluminum. A high AMIS value in the near surface layers of specimens subjected to procedures that may induce surface damage has been shown to correlate with a reduction in low-cycle fatigue life. Furthermore, AMIS may be used to estimate plastic strain accumulation when calibrated to specimens tested at a known plastic strain. In the current study, the effect of slip displacement amplitude and number of fretting cycles on the evolution of fretting damage is quantified using AMIS. Additional supporting evidence of significant plastic strain accumulation in the near surface layers of the fretted specimens obtained using nanoindentation and energy dispersive X-ray analysis (EDX) will also be presented. An opportunity exists to directly link microstructural damage measures such as AMIS with life prediction procedures, and therefore, remaining challenges in developing such methods will be discussed.
30.
Neumann, B. (2000). "Texture development of recrystallized quartz polycrystals unravelled by orientation and misorientation characteristics." Journal of Structural Geology 22(11-12): 1695-1711.
The development of microstructures and textures (i.e. crystallographic preferred orientations) during recrystallisation of naturally deformed quartz polycrystals has been studied via electron diffraction techniques in the scanning electron microscope. In the investigated sample series of quartz-rich rocks originating from different deformation regimes, the microstructural and textural changes in quartz have been significantly influenced by dynamic recrystallisation. Based on microstructural observations paired with orientation and misorientation analyses down to the scale of grains and subgrains, criteria could be established which characterise the dominant recrystallisation process and its influence on texture development. It is shown that the texture development during dynamic recrystallisation is controlled by a differential activation of slip systems in grains of ‘soft’ and ‘hard’ orientations. The analyses provide further evidence that specific grain orientations are preferred during crystal plastic deformation, recrystallisation and grain growth. The influence of twinning after the Dauphiné law was also investigated. Observations of a progressive reduction in the population of Dauphiné-twin boundaries during recrystallisation and a penetrative deformation in both hosts and twins indicate a generation prior to deformation and recrystallisation. A mechanical origin for twinning and possible influence on texture development was therefore discarded.
31.
Newbury, D. E. and D. B. Williams (2000). "The Electron Microscope: The Materials Characterization Tool of the Millenium." Acta Materialia 48(1): 323-346.
Transmission and scanning electron microscopes (TEM and SEM) together offer the most complete tool available for the characterization of materials. This combination of TEM and SEM provides surface and internal imaging of all solid materials over a magnification range from 20,000,000x down to 1x, with routine atomic resolution available at the high end and extraordinary depth of focus at the low end. The availability of x-ray spectometry on both instruments and electron spectometry on TEMs gives quantitative analysis capabilities covering the whole periodic table [above atomic number (Z)=2], at spatial resolutions from the micrometer to the nanometer scale for analytical sensitivities close to the single-atom level. Complementry electron-diffraction techniques for crystallographic measurements are standard on both instruments. For more than 40 years, since the development of thin-foil preparation techniques, the TEM has grown in versatility and power to the point where it is an indespensible part of a materials research laboratory. Since its commercialization in the mid-1960's, the SEM has revolutionized the study of fracture surfaces and, more recently, made crucial contributions to the science and engineering of microelectronic devices to the point where it is an essential presence on commercial fabrication lines. Using references to papers in Acta Mettalurgica/Materilia where possible, some of the major contributions of the TEM and SEM to our understanding of materials are looked back at and a few speculations on where electron microcroscopy of materials is going in the future are ventured.
32.
Newman, J., W. M. Lamb, et al. (1999). "Deformation processes in a peridotite shear zone: reaction-softening by an H2O-deficient, continuous net transfer reaction." Tectonophysics 303(1-4): 193-222.
The Turon de Técouère peridotite, in the North Pyrenean Zone, is composed of protomylonites grading to a 20–40 m wide zone of ultramylonites within a 0.6 km diameter exposure. The progressive mylonitization is marked by increasing volume fractions of very fine-grained matrix that comprise up to 90% of the ultramylonite. Deformation of the fine-grained matrix took place by grain size sensitive creep, as suggested by a very fine grain size (<10 μm), lack of dislocations in matrix grains, a weak crystallographic preferred orientation, and the alignment of grain boundaries parallel to the foliation. As the percentage of fine-grained matrix increased, weakening and localization resulted from a change in the dominant deformation mechanism from dislocation creep in the porphyroclasts to grain size sensitive creep in the fine-grained matrix. Production of the matrix grains took place by the nucleation of a number of different phases at the margins of porphyroclasts, indicating that the grain size reduction resulted primarily from reaction, and not from dynamic recrystallization. The nucleation of many phases along a single porphyroclast margin can be explained by a syntectonic continuous net transfer reaction associated with the spinel- to plagioclase-lherzolite transition. This continuous net transfer reaction produced new matrix grains with the same mineralogy as the original assemblage (olivine, orthopyroxene, clinopyroxene, spinel), with new compositions, plus plagioclase. Preliminary geothermobarometry indicates that the reaction took place over a range of temperatures and pressures (750–850°C, and possibly as high as 950°C and 0.5–1.1 GPa). The presence of only small amounts of amphibole, the lack of primary fluid inclusions, and no relation between the presence of amphibole and the intensity of mylonitic deformation led Vissers et al. [Tectonophysics 279 (1997) 303–325] to conclude that the deformation took place in an H2O-deficient environment. Reaction-enhanced softening may occur in the upper mantle wherever rocks move in pressure–temperature space and cross-reaction boundaries. Reaction boundaries are often modeled as univariant (lines in pressure–temperature space), yet mantle minerals are solid solutions so that reactions are continuous (multivariant) and take place over a broader region of pressure–temperature space than end-member reactions. It is therefore likely that shear zone deformation in polymineralic rocks will involve reaction-enhanced ductility over much of pressure–temperature space in the lithospheric mantle.
33.
Nibur, K. A. and D. F. Bahr (2003). "Identifying slip systems around indentations in FCC metals." Scripta Materialia 49: 1055-1060.
Atomic force and orientation imaging microscopy can be used to identify slip planes responsible for slip step formation around indentations in FCC polycrystalline engineering alloys. The character of the slip steps provides insight into the material's slip mode and the step patterns can be used to study dislocation reactions.
34.
Nicolaou, P. D., J. D. Miller, et al. (2005). "Cavitation during Hot-Torsion Testing of Ti-6Al-4V." Metallurgical and Materials Transactions A 36A(12): 3461-3470A.
Hot-torsion testing was used to establish the cavitation behavior of a typical alpha/beta titanium alloy, Ti-6Al-4V, with a colony microstructure, during simple-shear deformation. For this purpose, sections of deformed specimens were examined by optical metallography, and by scanning and orientationimaging microscopy (OIM). It was found that cavity nucleation occurred along prior beta boundaries as well as at triple points; in particular, most cavities nucleated along boundaries perpendicular to the axial direction of the specimen. Extensive growth was observed for cavities surrounded by both hard and soft orientations, with the soft colonies accommodating more of the imposed strain. At high degrees of deformation, dynamic globularization of the colony microstructure adjacent to the cavities was also observed. In addition, the metallographic observations revealed that the cavities did not grow in an equiaxed mode, but in an elliptical manner. A tensor describing the cavity-growth rate along the axial, radial, and hoop specimen directions was determined using measurements of individual cavity sizes. The cavity-growth behavior in torsion was compared to previous observations from hot-tension tests. This comparison indicated that the rate of cavity growth in shear was approximately one-tenth that in uniaxial tension. This finding is in broad agreement with models predicting the variation of the cavity-growth rate as a function of the ratio of the mean stress to the hydrostatic stress.
35.
Nicoletti, E. S. M., A. L. Pinto, et al. (2003). Thermally activated precipitation in a Ni-Cr-Mo superalloy. Anais do 58DG Congresso Anual da Associacao Brasileira de Metalurgia e Materiais, Rio de Janeiro, Brasil, Associacao Brasileira de Metalurgia e Materiais.
A Ni base superalloy (59%Ni, 23%Cr, 16%Mo) developed for corrosion resistant applications in both oxidizing and reducing atmospheres has been occasionally presenting pit corrosion, associated with significant reduction in electric resistivity, in the heat affected zone of welded plate joints. In an effort to contribute to the understanding of the mechanisms responsible for this degradation, the present study was undertaken with the purpose of investigating thermally activated second phase precipitation in the alloy. Aging treatments were performed at 700 and 900 deg C for time intervals of 1, 10 and 100 hours. Specimens for optical and scanning electron microscopies, taken from the heat treated alloy, were prepared metallographically before they were electrolytically etched. For transmission electron microscopy (TEM) study, specimens were thinned mechanically and then perforated electrolytically. Scanning electron microscopy (SEM) investigation was carried out using secondary as well as back scattered electrons, and also making use of electron back scattered diffraction (EBSD) technique. TEM analysis, on the other hand, involved the observation of phase contrast and selected area electron diffraction (SAED) patterns. The present of Mo-rich intergranular as well as intergranular precipitates was detected and their formation was attributed to the occurrence of ordering reactions common in Ni-Mo alloys. The formation of these precipitates results in the depletion of Mo and Cr in the alloy matrix and this leads to the degradation in corrosion resistant. The first step towards the precipitation process was detected by the appearance in the SAED pattern of the characteristic reflections from {420} planes, which was then followed by the development of superlattice based structure. Crystallographic and stoichiometric characteristics of these precipitates are currently being under investigation.
36.
Nielsen, S. F., E. M. Lauridsen, et al. (2001). "A three-dimensional X-ray diffraction microscope for deformation studies of polycrystals." Materials Science and Engineering A 319-321: 179-181.
The microstructure in polycrystalline materials has mostly been studied in planar sections by microscopy techniques. Now the high penetration power of hard X-ray synchrotron radiation makes three-dimensional (3-D) observations possible in bulk material by back tracing the diffracted beam. The three-dimensional X-ray diffraction (3DXRD) microscope installed at the European Synchrotron Radiation Facility in Grenoble provides a fast and non-destructive technique for mapping the embedded grains within thick samples in three dimensions. All essential features like the position, volume, orientation, stress-state of the grains can be determined, including the morphology of the grain boundaries. The accuracy of this novel tracking technique is compared with electron microscopy (EBSP), and its 3-D capacity is demonstrated.
37.
Nikoobakht, B. V., M. D.; Stranick, S. J. (2005). A new approach for fabricating horizontally grown semiconductor nanowires (case of zinc oxide). 2005 International Semiconductor Device Research Symposium, Bethesda, Maryland, USA.
The positioning and directed assembly of semiconductor nanowires (NWs) is of considerable current interest for "bottom-up" approaches to the engineering of intricate structures from nanoscale building blocks. In this presentation, a new technique for growth of horizontal ZnO NWs on (1120) sapphire surface is discussed, which provides the in situ alignment and predictable positioning of ZnO NWs. This strategy allows for the large scale assembly of NWs, diameter control, and production of quantum wires. A crystallographic model explaining the unique growth direction of Ý1100¨ is proposed, which is supported by electron-back scattering diffraction results. Two photon photoluminescence microscopies of oriented NWs with diameter less than 5 nm as well as the factors controlling the NW growth direction are discussed.
38.
Ning, H., B. J. Duggan, et al. (1996). The Effect of Shear Bands on the Evolution of Recrystallization Texture in Pure Iron. Eleventh International Conference on Textures of Materials, Xi'an, China, International Academic Publishers.
39.
Nitta, H., Y. Iijima, et al. (2004). "Grain boundary self-diffusion in directionally solidified equiatomic Fe–Co alloy." Materials Science and Engineering A 382(1-2): 250-256.
Grain boundary diffusivities of 59Fe and 57Co in a binary Fe-50 at.%Co alloy have been determined at a temperature range between 883 and 1123 K by serial sputter-microsectioning technique using specimen unidirectionally solidified at three different solidification rates of 12000, 60 and 32 mm/h. Above the order–disorder transformation temperature of 1003 K, the Arrhenius plots of the grain boundary diffusivities in the alloy solidified at three rates show straight lines. The diffusivities in the specimen with 32 mm/h are higher than those with 60 and 12000 mm/h. Below 1003 K, all the Arrhenius plots of the diffusivities show downward curvature remarkably owing to the atomic ordering. From the analysis of depth profiles, the atomic ordering gives large influence on the diffusion along subgrain boundaries rather than the diffusion along random grain boundaries.
40.
Nogita, K. and A. K. Dahle (2001). "Eutectic growth mode in strontium, antimony and phosphorous modified hypoeutectic Al-Si foundry alloys." Materials Transactions 42(No. 3): 393-6.
41.
Nogita, K. and A. K. Dahle (2001). "Eutectic solidification in hypoeutectic Al-Si alloys: electron backscatter diffraction analysis." Materials Characterization 46(4): 305-10.
Nucleation and growth of the eutectic in hypoeutectic Al–Si foundry alloys has been investigated by the electron backscatter diffraction (EBSD) mapping technique using a scanning electron microscope (SEM). Sample preparation procedures for optimizing mapping have been developed. To obtain a sufficiently smooth surface from a cast Al–Si eutectic microstructure for EBSD mapping, an appropriate preparation technique by ion milling was developed and applied instead of conventional electropolishing. By comparing the orientation of the aluminum in the eutectic to that of the surrounding primary aluminum dendrites, the growth mechanism of the eutectic can be determined. Two different results were found, in isolation or sometimes together, but distinct for different strontium contents: (1) crystallographic orientations of aluminum in eutectic and surrounding primary dendrites are identical, and (2) wide variation in orientations of the aluminum in the eutectic.
42.
Nogita, K., A. Knuutinen, et al. (2001). "Mechanisms of eutectic solidification in Al–Si alloys modified with Ba, Ca, Y and Yb." Journal of Light Metals 1: 219-228.
The eutectic solidification mechanisms in an A356.0 (Al–7% Si–Mg) alloy modified by barium, calcium, yttrium and ytterbium have been determined. The crystallographic orientations of aluminium in the eutectic and the surrounding aluminium dendrites were measured by electron backscattering diffraction mapping, and samples were also quenched at different stages during the eutectic arrest and examined by optical microscopy. The combination of these two techniques shows that each of the elements added promote heterogeneous nucleation of eutectic grains in the interdendritic liquid, while the aluminium in the unmodified alloy grows epitaxially from the dendrites. Furthermore, calcium and yttrium result in a strong dependency of eutectic solidification on the thermal gradient, i.e. the eutectic evolves from the walls towards the centre of the sample on a macro-scale. These differences in eutectic solidification mode show a correlation with some thermal characteristics of the eutectic arrest.
43.
Nohava, J., P. Hausild, et al. (2002). "Electron backscattering diffraction analysis of secondary cleavage cracks in a reactor pressure vessel steel." Materials Characterization 49(3): 211-217.
An analysis of secondary cleavage cracks in the A 508 C1.3 bainitic steel has been carried out using electron backscattering diffraction (EBSD) and scanning electron microscopy (SEM). The crystallographic orientation in the vicinity of the secondary cracks was studied. Secondary cleavage crack propagation planes were identified to be {100}, {110}, {112} and {123}. The secondary cracks propagated mostly in the range of one crystallographic grain (bainitic packet) and were arrested on high-angle twist type boundaries or in the upper bainite carbide colonies. The size of cleavage facets on the fracture surface corresponds to the size of the bainitic packets.
44.
Nolze, G. (2004). "Characterization of the fcc/bcc orientation relationship by EBSD using pole figures and variants." Zeitschrift fur Metallkunde 95(9): 744-755.
The orientation relationship (OR) between fcc and bcc lattices are described by crystallographic fundamentals using the example of Kurdjumov-Sachs (K-S) and Nishiyama-Wassermann (N-W). Complete pole figures containing all variants will be used to distinguish even between slightly different ORs. EBSD on iron meteorites and duplex steel has been used to analyse a large number of crystal orientations with regard to a high statistical significance and a high probability to capture all variants in a single measurement. It is shown that the use of fixed OR models like K-S, N-W, Bain, Pitsch, or Greninger-Troiano does not satisfacturally reflect the observed experimental pole distributions. It is not convenient to use high-indexed lattice planes and directions to describe the small deviations from the given models. The Euler subspace representation offers a readily comprehensible tool to get an idea about the characteristic of the experimentally detected OR.
45.
Nolze, G. (2006). "Improved determination of fcc/bcc orientation relationships by use of high-indexed pole figures." Crystal Research and Technology 41(1): 72-74.
The use of variants to analyze fcc/bcc orientation relationships is demonstrated by EBSD data. Because of multiply occupied poles in the stereographic projections low indexed pole figures are not always suitable. This is mostly caused by the convolution of all scattered individual orientation data as the single poles cannot resolved in the pole figure. Pole figures of higher indexed lattice planes more reliably reflect the character of the orientation relationship since no overlapping of poles occurs.
46.
Nolze, G. (2006). "Some geometrically caused image distortions effects and their influence on the interpretation of EBSDmeasurements." Materials Science and Technology(pre-print).
The imaging of high-tilted flat sample surfaces in scanning electron microscopy (SEM) has some special characteristics. A typical example is the trapezium distortion which is only detectable at low magnifications. In contrast to this a rhomboidal distortion is discussed in the present paper which appears independent from the magnification used. Rhomboidal distortion is also caused by a simple geometric misalignment, an additional slight tilt of the sample surface out of the plane of the microscope stage or the pretilted sample holder. The rhomboidal distortion may effect all image-related orientation descriptions, e.g. also a texture characterisation. In order to draw attention to this unexpected influence some typical examples are given and a simplified solution is proposed.
47.
Nolze, G. and V. Geist (2004). "A new method for the investigation of orientation relationships in meteoritic plessite." Crystal Research and Technology 39(4): 343-352.
The orientation relationship (OR) between the bcc and fee phase in the plessite microstructure of the iron meteorites Watson, Agpalilik and Gibeon has been analysed in a scanning electron microscope using electron back-scattered diffraction (EBSD). A very strong OR exists, independently on the analysed plessite type and the observed spreading of single orientation data. The agreement between the experimental orientation distribution and existing models varies for each meteorite. The black plessite in the Agpalilik corresponds to the Nishiyama-Wassermann model whereas the duplex plessite of the Gibeon meteorite shows an OR close to the Kurdjumov-Sachs model. The Watson meteorite is strongly deformed so that a general OR is difficult to determine due to the blurred experimental orientation distribution.
48.
Nolze, G., V. Geist, et al. (2005). "Investigation of orientation relationships by EBSD and EDS on the example of the Watson iron meteorite." Crystal Research and Technology 40(8): 791-804.
The suitability of the electron back-scatter diffraction technique (supported by EDS) in order to study the complex microstructures of iron meteorites is demonstrated on the example of the Watson meteorite. The orientation relationships between the main phases kamacite, taenite and schreibersite/rhabdite as well as effects of the real structure have been investigated. In kamacite bands highly deformed blocks appear which show a continous change of orientation. Plessitic regions are surrounded by deformed taenite lamellae. Also these lamellae show the typical M-profile of the Ni concentration in cross section. In the center a martensitic microstructure has been proven. The white plessite is characterized by a high number of individual kamacite grains which however are separated mainly by low-angle boundaries. So an orientation clustering occurs. The determination of orientation relationships was only possible for a single plessite region comparing the intensity distribution in pole figures with simulations. Schreibersite is brittle and shows a high number of microcracks. However, the strong deformation of kamacite does not allow us to decide whether an orientation relationship between the phosphides and the surrounding kamacite exists or not.
49.
none (2004). "Research trend on ultrafine grained light metals (from a viewpoint of physical metallurgy)." Materia Japan 43(5): 405-410.
In addition to light metals, the research on ultrafine grained crystals have been going on for ferrous, copper and others as well. The Severe Plastic Deformation (SPD) method has brought great success in this regard to aluminum alloys and based on reported results thus far, ultrafine grains of less than 1mum structures are obtained uniformly. Several SPD techniques have been proposed within which the greatest results have been obtained from Equal Channel Angular Extrusion (or Pressing), (ECAE, or ECAP), Accumulative Roll Bonding (ARB) and Cyclic Extrusion and Compression (CEC) techniques. Utilizing ARB technique, authors were successful in obtaining relative strain of up to 4.8 on 1100-Al for which the Electron Back Scattering Pattern (EBSP) results are provided with discussion. In these structures, the discontinuous crystallization does not occur, rather the structure displays a prominent continuous crystallization. Several TEM images and illustrations of grain subdivisions with interconnecting boundaries (GNB and IDB) are provided.
50.
none (2005). Chemical indexing software automates filtering process. Advanced Materials and Processes. 163: 17-18.
ChI-Scan is a chemical indexing software package designed to reliably differentiate between phases that are similar crystallographically but differ in chemical composition. The software, which is an integral part of the Edax Pegasus microanalysis system, takes advantage of the Pegasus platform for simultaneous collection of energy dispersive spectroscopy (EDS) and EBSD data. (Edited abstract)
51.
none (2006). "EDS, EBSD and WDS microanalysis system.(EMERGING TECHNOLOGIES IN Forensic Science)." Laboratory Equipment 42(10): 38 (1).
By combining X-ray microanalysis (EDS), electron diffraction (EBSD) and wavelength dispersal spectrometry (WDS), the Trident System reduces or eliminates the need to compromise the performance of one toolto optimize another, depending on the scanning electron microscope'schamber configuration. In addition, all three techniques can be integrated into one PC environment. The system's hardware and software provides all three tools with data sharing and improves the speed and accuracy of data processing. EDS for elemental composition (chemistry)and EBSD for crystallography (structure) have been used together or separately on the same system for the analysis of a material. EDAX Inc. www.edax.com, 201-529-4880
52.
Novillo, E., D. Hernández, et al. (2004). "Analysis of ferrite grain growth mechanisms during g-a transformation in a niobium alloyed steel using EBSD." Materials Science and Engineering A 385(1-2): 83-90.
The austenite to ferrite phase transformation was studied in a C–Mn–Nb steel after different hot deformation schedules, leading to deformed and recrystallized austenite. The mechanisms of nucleation and growth of ferrite grains were investigated by means of the electron back scattered diffraction (EBSD) technique. The ferrite microstructures were characterised in terms of the misorientation angles between ferrite grains and the deviations from an ideal Kurdjumov–Sachs orientation relationship with the austenite. The results show that the grain refinement produced by the accumulation of the deformation in the austenite is limited to a certain extent by the ferrite grain coarsening taking place behind the transformation front. Both coalescence and normal grain growth have been observed to contribute to this coarsening. Coalescence is enhanced as a result of the variant selection taking place in transformation from a recrystallized austenite. The accumulation of the deformation in the austenite results in ferrite–ferrite boundaries of higher misorientation, causing coalescence in this case to be less favoured, as compared with normal grain growth.
53.
Novillo, E., M. M. Petite, et al. (2003). "Texture and Microtexture Evolution in an Ultra-Low Carbon Steel During Recrystallization." Advanced Engineering Materials 5(8): 575-578.
Recrystallization texture and microtexture in a cold-rolled ultra-low carbon steel were investigated using X-ray diffraction and electron backscattered diffraction based orientation imaging microscopy (EBSD/OIM). Aspects such as nucleation, evolution of the volume fraction, and grain size were considered. Recrystallization and texture evolution during continuous annealing of cold-rolled low-carbon steel have been studied by many authors. A strong gamma -fiber texture appears to be responsible for the high formability in low-carbon steels. Two main theories based on oriented nucleation and selective growth have competed for an interpretation of texture development and some attempts have also been made to find complementary approaches based on advantage in frequency or size. EBSD techniques have been used to analyze the evolution of the grain size and volume fraction of certain texture components during the recrystallization process. The material used was an ultra-low carbon steel whose composition is shown in Table 1. This steel was industrially produced and processed by casting to about 85 % cold reduction.
54.
Novillo, E., M. M. Petite, et al. (2004). "Analysis of recrystallization and grain growth in ultra low carbon steels using EBSD." Revista de Metalurgia (Madrid) 40(5): 352-358.
This work is focused on the study of recrystallization texture and microtexture in a cold rolled ultra low carbon steel and its relationship with the global texture. Aspects like nucleation, evolution of the volume fraction and grain size were considered. An important grain selection associated with a significant size and number advantages of the {111} recrystallized grains is observed. This grain selection gives rise to the development, at the latest stages of recrystallization, of a strong gamma-fibre associated to good drawing properties.
55.
Nowack, E. R., J. M. Fabijanic, et al. (1998). "Low-Temperature Magnetic-Relaxation in Hgba2Ca2Cu3O8+delta Single-Crystals with Columnar Defects." Physical Review B 58(9): 5825-5830.
56.
Nowell, M. M. (1998). "Texture and Grain Boundary Structure Dependence of Hillock Formation in Thin Metal Films." Materials Research Society Symposium Proceedings 516: 115-120.
The development of hillocks on metal films during annealing is detrimental to downstream processing of integrated circuit structures. This work focuses upon the local character of textureand grain boundary structure near hillocks in metal films. It is apparent from the results that local grain boundary structure and texture strength are important parameters in identifying locations in the films that are preferentially susceptible to failure under given conditions. Results in aluminum and platinum films indicate that non-(111)oriented grains preferentially contain hillocks. In addition, (111) oriented grains with boundaries characterized by high angle rotations about random axes are prone to hillock formation.
57.
Nowell, M. M. (2002). "Ion Beam Preparation of Passivated Copper Integrated Circuit Structures for Electron Backscatter Diffraction/Orientation Imaging Microscopy Analysis." Journal of Electronic Materials 31(1): 23-32.
Passivation layers were removed from copper interconnect lines using a broad beam ion source in preparation for electron backscatter diffraction (EBSD) and orientation imaging microscopy (OIM) analysis. Results were obtained on interconnect lines with widths as small as 0.25µm. The effects of ion beam energy and scanning electron microscope (SEM) acceleration voltage on the quality of the results obtained are examined and explained. The use of thin amorphous carbon coatings to reduce specimen charging during orientation data collection is also discussed.
58.
Nowell, M. M. and S. I. Wright (2001). Microtextural Characterization of Golf Club Heads. Materials and Science in Sports, TMS (The Minerals, Metals & Materials Society).
The properties of polycrystalline materials used in golf club head forming are known to be dependent on features of the microstructure such as grain size and/or shape that arise from the processing path. The dependency of properties on the crystallographic orientation of the constituent grains is less understood. Polycrystals exhibiting strong preferred orientation or texture tend to exhibit anistropic behavior. In order to gain some understanding in this arena, the distribution of crystallographic orientation within the polycrystalline microstructure has been characterized using automated electron backscatter diffraction in the scanning electron microscope. Data obtained from samples of cast and forged titanium and steel heads will be presented. Orientation maps constructed from the acquired data showing the spatial distribtion of orientation within the samples will be presented, and the texture and anistropy of the samples will be discussed.
59.
Nowell, M. M. and S. I. Wright (2004). "Phase differentiation via combined EBSD and XEDS." Journal of Microscopy 213(Pt 3): 296-305.
Electron backscatter diffraction (EBSD) and orientation imaging microscopy have become established techniques for analysing the crystallographic microstructure of single and multiphase materials. In certain instances, however, it can be difficult and/or time intensive to differentiate phases within a material by crystallography alone. Traditionally a list of candidate phases is specified prior to data collection. The crystallographic information extracted from the diffraction patterns is then compared with the crystallographic information from these candidate phases, and a best-fit match is determined. Problems may arise when two phases have similar crystal structures. The phase differentiation process can be improved by collecting chemical information through X-ray energy-dispersive spectroscopy (XEDS) simultaneously with the crystallographic information through EBSD and then using the chemical information to pre-filter the crystallographic phase candidates. This technique improves both the overall speed of the data collection and the accuracy of the final characterization. Examples of this process and the limitations involved will be presented and discussed.
60.
Nowell, M. M. and S. I. Wright (2005). "Orientation effects on indexing of electron backscatter diffraction patterns." Ultramicroscopy 103(1): 41-58.
Automated Electron Backscatter Diffraction (EBSD) has become a well-accepted technique for characterizing the crystallographic orientation aspects of polycrystalline microstructures. At the advent of this technique, it was observed that patterns obtained from grains in certain crystallographic orientations were more difficult for the automated indexing algorithms to accurately identify than patterns from other orientations. The origin of this problem is often similarities between the EBSD pattern of the correct orientation and patterns from other orientations or phases. While practical solutions have been found and implemented, the identification of these problem orientations generally occurs only after running an automated scan, as problem orientations are often readily apparent in the resulting orientation maps. However, such an approach only finds those problem orientations that are present in the scan area. It would be advantageous to identify all regions of orientation space that may present problems for automated indexing prior to initiating an automated scan, and to minimize this space through the optimization of acquisition and indexing parameters. This work presents new methods for identifying regions in orientation space where the reliability of the automated indexing is suspect prior to performing a scan. This methodology is used to characterize the impact of various parameters on the indexing algorithm.
61.
Nowell, M. M., D. P. Field, et al. (2004). In-Situ EBSD Investigation of Recrystallization in ECAE Processed Copper. Proceedings of the Joint International Conference on Recrystallization and Grain Growth, Materials Science Forum. B. Bacroix, J. H. Driver, R. LeGallet al. Aedermannsdorf, 4711, Switzerland, Trans Tech Publications Ltd. 467-470: 1401-1406.
The microstructural evolution of heavily deformed OFHC copper during recrystallization and grain growth was characterized in-situ by automated Electron Backscatter Diffraction (EBSD) or Orientation Imaging Microscopy (OIM). Successive scans (approximately 50-60 2 minute scans per sample) were performed on samples undergoing heating from ambient temperature to approximately 150-200 degrees C. The orientation and grain boundary textures of growing and shrinking grains are compared. The relationship between various indirect metrics of strain energy and the microstructural evolution are also investigated. These qualitative measures are obtained from OIM data and include parameters such as local misorientation and EBSD pattern quality.
62.
Nowell, M. M., R. A. Witt, et al. (2005). "EBSD Sample Preparation: Techniques, Tips and Tricks." Microscopy Today 13(4): 44-48.
63.
Nucci, J. A., R. R. Keller, et al. (1997). "Grain boundary misorientation angles and stress-induced voiding in oxide passivated copper interconnects." Applied Physics Letters 70(10): 1242-1244.
Grain boundary misorientations were determined by electron backscattering diffraction for tantalum-encapsulated, copper interconnects which contained thermal-stress-induced voids. The misorientation angles at voided and unvoided line segments were analyzed for two differently heat treated sample types, which were not equally susceptibile to stress voiding. Unvoided line segments contained a larger percentage of low misorientation angle, lower diffusivity boundaries than regions adjacent to voids. In addition, the more void resistant sample type also contained an overall higher proportion of low misorientation angle boundaries than the sample type which exhibited more voiding. The data provide further support for the importance of local variations in microstructure, which control the kinetics of stress void formation and growth.
64.
Nucci, J. A., R.R.Keller, et al. (1996). "Local crystallographic texture and voiding in passivated copper interconnects." Applied Physics Letters 69(26): 4017-4019.
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