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58 records found
1.
Réglé, H., N. Maruyama, et al. (2004). Texture and Microstructure of the Austenite in Multiphased Steel Sheets. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
In this paper we present results obtained in collaboration between NSC and Arcelor on the austenite of a multiphased steel and on a 70%Ni-30Fe alloy. The work concerns the formation of the crystallographic textures during the recrystallization of austenite, since these textures have a strong influence, after the phase transformation, on the forming properties of the sheets. The microstructure and the textures of the austenite and the FeNi alloy were measured with X-ray diffraction techniques and with EBSD on a high resolution FEG-SEM.
2.
Römer, J., G. Beuchle, et al. (2003). "In situ investigation of U(IV)-oxide surface dissolution and remineralization by electrochemical AFM." Journal of Nuclear Materials 322(1): 80-86.
Surface chemical processes of UO2 are investigated on a nanoscopic scale by electrochemical atomic force microscopy (ECAFM) using a home-developed electrochemical cell. Dissolution reactions of the solid surface and subsequent remineralization are observed at the solid-water interface under different redox conditions and carbonate concentrations. The local dissolution rates vary between different grain faces, grain boundaries and etch pits. A correlation between dissolution rates and the grain orientations relative to the specimen surface can be demonstrated by electron backscatter diffraction (EBSD). Remineralization under oxidizing conditions occurs mainly at grain faces with higher dissolution rates. The remineralized products are particles of 200-900 nm in diameter and exhibit a tabular morphology. Profound knowledge of the UO2 surface chemistry on a nanoscale may help to clarify the related mechanisms explaining the macroscopically observed dissolution rates. Copyright 2003 Elsevier B.V. All rights reserved.
3.
Randle, V. and B. Ralph (1988). "Application of Electron Back Scattering to the Measurement of Grain Misorientation Texture." Institute of Physics Conference Series(93): 231-232.
4.
Randle, V. and B. Ralph (1988). "Local Texture Changes Associated with Grain-Growth." Proceedings of The Royal Society of London Series A 415(1848): 239.
5.
Randle, V. and G. L. F. Powell (1993). "Application of electron backscatter diffraction to orientation measurements of individual carbides in a white cast-iron." Journal of Materials Science 12(10): 779-81.
Models were formulated in an effort to characterize recrystallization in materials with multiple texture components. The models are based on a microstructural path methodology (MPM). Experimentally the microstructural evolution of commercial aluminum during recrystallization was characterized using stereological point and lineal measurements of microstructural properties in combination with EBSP analysis for orientation determinations. The potential of the models to describe the observed recrystallization behavior of heavily cold-rolled commercial aluminum was demonstrated. A successful MPM model was deduced which, for each texture component-random, rolling and cube orientations, was quantitatively consistent with the measured microstructural properties. Nucleation and growth rates were deduced for each texture component using the model. (32 References).
6.
Randle, V. and G. Laird (1993). "A Microtexture Study of Eutectic Carbides in White Cast Irons Using Electron Backscatter Diffraction." Journal of Materials Science 28(15): 4245-4249.
7.
Randle, V. and G. Owen (2006). "Mechanisms of grain boundary engineering." Acta Materialia 54(7): 1777-1783.
This paper reports new data for the analysis of grain boundary misorientation populations and microstructure characteristics in grain boundary engineering (GBE) copper, accompanied by parallel measurements in a non-GBE control specimen of the same material. The GBE processing resulted in a doubling the number fraction of Σ3 boundaries to 41%, accompanied by a 12 times increase in Σ9. The Σ3 population has a convoluted morphology, indicating a range of boundary planes and associated mobilities, and moreover indicating that such Σ3s arise from Σ3n interactions. Many Σ3s become incorporated into the grain boundary network. Hence, the grain boundary network is modified directly via partial replacement by Σ3s. This is termed the ‘Σ3 regeneration mechanism’. The data from the GBE copper were compared with data previously acquired from GBE brass. The brass has approximately the same number fraction of Σ3s (38%), but a lower number fraction of Σ9s and Σ27s and a markedly different microstructure where twins are not incorporated into the grain boundary network and instead the network is modified indirectly via the modification to the boundary crystallography that results from twinning. This is termed the ‘new twinning’ mechanism. It is suggested that these two mechanisms are general for all GBE metals where the GBE is based on annealing twinning. After the condition of a minimum number fraction (≈20%) of Σ3s is met, the proportion of each mechanism that operates will be governed by processing variables, e.g., cold deformation level and annealing time/temperature.
8.
Randle, V. and S. Vale (1997). "Mapping microstructures." Materials World 5(10): 574-576.
Electron backscatter diffraction in the scanning electron microscope provides information on grain boundary statistics for microstructural crystallography and is also used in crystal orientation measurements. The most recent development of this technique is crystal orientation mapping (COM), maps from which reveal the true microstructure of the material, and provide new insights by relating the crystallographic structure to other microstructural features such as cracks or chemistry. The applications of COM are categorized as: spatial distribution of texture components, misorientations and interfaces, orientation perturbations within grains, true grain size/shape distributions, and deformation maps from diffraction pattern quality parameters.
9.
Randle, V., B. Ralph, et al. (1988). "The Relationship Between Microtexture and Grain-Boundary Parameters." Acta Metallurgica 36(2): 267-273.
10.
Randle, V., B. Ralph, et al. (1989). "Measurement of Lattice-Parameter and Strain Using Convergent Beam Electron-Diffraction." Journal of Electron Microscopy Technique 13(1): 51-65.
11.
Rangaswamy, P., M. A. M. Bourke, et al. (2002). "A Study of Twinning in Zirconium Using Neutron Diffraction and Polycrystalline Modeling." Metallurgical and Materials Transactions A 33(March): 757-763.
An experimental study using neutron diffraction quantified the evolution of twinning in pure clock-rolled zirconium that was subseqently deformed under uniaxial compression. The clock rolling introduced an initial texture of approximately 5 times random, and the compression specimens were cut with their loading axes nearly parallel to the predominant c-axes direction. Seven specimens deformed to strains between -2 and -17 pct and an undeformed specimen (0 pct strain) were examined. The deformation was performed at an applied strain rate of 0.001/s at 77 K. Twin volume fractions were estimated from diffraction data. Changes in texture and twin volume fractions were compared to predictions from a visco-plastic self-consistent (VPSC) polycrystal model, which described both slip and twinning. These results help benchmark the polycrystalline model, validate the description of twinning, and potentially lead to a better understanding of its role in hardening.
12.
Rao, G. B., J. Q. Wang, et al. (2006). "Study of residual stress accumulation in TiNi shape memory alloy during fatigue using EBSD technique." Materials Letters 60(6): 779-782.
In this study, electron backscatter diffraction (EBSD) technique was applied to study the residual stress accumulation of TiNi shape memory alloy (SMA) during fatigue process, which caused the degradation of the shape memory effect (SME) and super-elasticity (SE). From the analysis of the pattern quality change before and after fatigue test, it showed that, with the stress-induced martensitic transformation (SIMT) during loading process and reverse SIMT during unloading process in each loading cycle, residual stress was accumulated in the parent phase. The results also showed that the residual stress distribution was not uniform inside one grain and between grains. TEM observation showed only dislocation increasing, no persistent slip band (PSB) was found, showing that the non-uniformity of the residual stress distribution was not caused by PSB.
13.
Rasmussen, A. A., A. Gholinia, et al. (2004). Thermal Stability of Electrodeposited Ni and Ni-Co Layers; an EBSD-Study. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
The influence of heat treatment on the microtexture of electrodeposited Ni and Ni-Co layers was investigated with electron backscatter diffraction (EBSD) with high resolution. Samples were annealed for 1 hour at 523 K and 673 K, the temperature region wherein recrystallisation occurs. The results are discussed in relation to the resolution of EBSD for the very fine grained electrodeposits and previous X-ray diffraction investigations.
14.
Ratchev, P., B. Verlinden, et al. (1999). Texture evolution during hot plane strain compression of a hot deformed AA5182 Al-Mg alloy. Twelfth International Conference on Textures of Materials (ICOTOM 12), McGill University, Montreal, Canada, NRC Research Press.
15.
Rau, B., I. Sieber, et al. (2003). Homo-epitaxial Si absorber layers grown by low-temperature ECRCVD. Proceedings of Symposium D on Thin Film and Nano-Structured, Strasbourg, France.
We studied the homo-epitaxial growth of Si absorber layers at temperatures of 420-560 ding the C by electron-cyclotron resonance chemical vapour deposition. We deposited the Si films at rates of 15 nm min-1 on (1 0 0)-, (3 1 1)-, (1 1 1)- and multicrystalline Si wafers. Both substrate temperature and orientation have a pronounced influence on the structural quality. On Si(1 0 0) substrates films grew epitaxially above 480 ically is C and are of excellent crystallographic quality up to thicknesses of 2.5 µm. On Si(3 1 1) the epitaxy breaks down rapidly by the formation of polycrystalline regions. On Si(1 1 1) the films are always fine polycrystalline. Using multicrystalline substrates the quality of the films is related to the orientation of the grains ranging from excellent epitaxy to pure fine polycrystalline growth. The electrical properties of the intentionally undoped films grown on Si(1 0 0) are discussed in relation to the crystal quality.
16.
Raza, B. and D. B. Holt (1995). "EBIC studies of grain boundaries." Microscopy of Semiconducting Materials.
We have investigated the morphology of the non-reactive solid state diffusion bonded interfaces between polycrystalline copper and single crystal zirconia of (100) and (110) orientations. The bonded interfaces showed regular faceted voids on the Cu side. The angles of the faceted void edges to the 001 direction of the ZrO2 is dependent on the crystallographic orientation of the ZrO2. To examine the relationship between the Cu grains that showed faceted voids and the ZrO2, the orientation of the Cu grains were measured using Electron Back Scattering Diffraction (EBSD) in the scanning electron microscope. These misorientations are shown in a Frank-Rodrigues map and the dependence on bonding conditions is discussed. (5 References).
17.
Read, D. T., Y. W. Cheng, et al. (2004). "Morphology, microstructure, and mechanical properties of a copper electrodeposit." Microelectronic Engineering 75(1): 63-70.
This paper presents two new experimental observations on electrodeposited copper: unusual morphology as seen in the scanning electron microscope at high magnification, and mechanical properties, as measured by tensile testing. We report detailed characterization of a 2.6 µm thick copper electrodeposit, made on silicon using laboratory procedures and similar to materials now widely used in advanced electronic interconnect structures. The microstructure was characterized by X-ray diffraction, electron backscattered diffraction, imaging in a field emission scanning electron microscope (FESEM), and microtensile testing. Initial observations indicated microstructural dimensions and mechanical properties in the expected ranges. However, using high-magnification, high resolution imaging in the FESEM, we found a surprising result: the morphology of this electrodeposit resembled an agglomeration of round balls or spheres approximately 30-50 nm in diameter. Both X-ray and electron diffraction results showed grain and subgrain sizes much larger than the individual spheres. Molecular dynamics (MD) simulations of spheres of copper atoms were carried out to interpret the observations, and produced a degree of interpenetration of the spheres that was consistent with the observations. However, in MD simulations of two initially misoriented spheres of up to a thousand atoms, with diameters up to 3 nm and for durations up to 30 ps, the spheres readily agglomerated but remained misoriented. So, the mechanism and rate of crystallographic grain growth within the agglomeration of spheroids remains unknown. This unusual spheroidal morphology may be related to the unusual room-temperature grain growth observed in electrodeposited copper.
18.
Reimer, L., U. Heilers, et al. (1986). "Kikuchi band contrast in diffraction patterns recorded by transmitted and backscattered electrons." Scanning 8(3): 101-118.
A theoretical model is presented for explaining Kikuchi band contrast which uses only the primary and the final Bloch-wave fields when the electron wave enters and leaves the specimen, respectively. The intermediate multiple scattering is treated incoherently. This model can explain the contrast reversal of Kikuchi band contrast from excess to defect type with increasing foil thickness in TEM. The same model can be used to calculate the intensity variation across Kikuchi bands in electron channelling patterns (ECP) and electron backscattering patterns (EBSP) recorded from solid specimens in SEM. Corresponding experimental results agree with calculations. Dynamical multi-beam calculations for a systematic row of Bragg reflections result in excess Kikuchi band profiles that can be compared with ECP or EBSP records. These calculations show that it is essential to use the dependent rather than the independent Bloch-wave model. (62 References).
19.
Reis, A. C. and L. Kestens (2004). Cross-sectional texture gradients in interstitial free steels processed by accumulated roll bonding. 2nd International Conference on Texture and Anisotropy of Polycrystals (ITAP 2), Metz, France, Balaban Publishers; Scitec Publications.
An interstitial-free steel was severely plastically deformed in an accumulative roll bonding (ARB) experiment with 10 consecutive passes applied at 480 degrees C. Nominal reductions of 50% per pass and an intermediate annealing treatment of 5 min. at 520 degrees C were employed. A total true strain of epsilonvM = 8.00 was applied, which corresponds to an accumulated reduction of 99.9%. The evolution of texture and microstructure was monitored by means of orientation imaging microscopy. A lamellar microstructure, characteristic of severely rolled sheet materials, was observed even after the highest strains. The average lamellar width was determined as a function of rolling strain. Under the experimental limitations in terms of spatial resolution, no significant difference was observed between the average lamellar width in the mid-section and near the surface of the sheet. Texture analysis revealed a conventional cross-sectional gradient with plane strain rolling components in the mid-layers and shear components in the subsurface regions. Although these different strain modes did not affect the microstructure in terms of the average lamellar spacing, an effect was observed on the average aspect ratio of the grains. This was much higher in the sheared (surface) layers than in the plane strain compressed (centre) areas. The surface structure did not have an effect, though, on the bulk microstructural evolution in spite of the specific nature of the ARB process during which the surface layer of one pass reappears in the mid-section of the next pass.
20.
Reis, A. C. C., K. L., et al. (2005). Lamellar Subdivision during Accumulative Roll Bonding of a Titanium Interstitial Free Steel. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
Titanium alloyed interstitial free steel was processed by means of accumulative roll bonding (ARB) in order to obtain an ultrafine grained structure. Ten consecutive rolling passes were applied at 480°C with a nominal reduction of 50% per pass and an intermediate annealing treatment of 5 min. at 500°C. A total true strain was obtained of εvM = 8.0 which corresponds to an accumulated reduction of 99.9%. Orientation imaging microscopy was used to evaluate textures and microstructures. A pronounced lamellar structure was observed until the 5th pass with an incidence of high angle grain boundaries predominantly parallel to the rolling direction. After the 6th pass (εvM = 4.8) an increased fragmentation perpendicular to the rolling direction starts to develop in spite of the lamellar microstructure with an average spacing of approximately 1 μm. From the 7th pass onwards (εvM ≥ 5.6) a random high angle grain boundary distribution develops which results in a more equi-axed ultrafine microstructure after the 9th pass (εvM = 7.2) with an average grain width of 200 nm. As the rolling is carried out without lubrication, the surface areas display a slightly more fragmented structure than the midlayer sections and typical shear texture components are present in these surface zones (<110>//ND and <211>//ND fibre). Although the sheets are stacked upon each other after each subsequent pass, the shear strain microstructural and textural features are rapidly decomposed in the midlayer in each subsequent rolling pass which is clearly revealed by the cross sectional orientation scan on the composite sample. Hence it cannot be concluded that the surface shear strain significantly contributes to the grain fragmentation in the bulk volume of the composite sample.
21.
Ren, S. X., E. A. Kenik, et al. (1997). Monte Carlo Simulation of Spatial Resolution for Electron Backscattered Diffraction (EBSD) with Application to Two-Phase Materials. Microscopy and Microanalysis, Cleveland, Ohio, Springer.
22.
Rey, C. and P. V. De Lesegno (1997). "Experimental analysis of bifurcation and post-bifurcation in iron single crystals." Materials Science and Engineering A 234-236: 1007-1010.
23.
Reyntjens, S. and C. Kubel (2005). "Scanning/transmission electron microscopy and dual-beam sample preparation for the analysis of crystalline materials." Journal of Crystal Growth 275(1-2): e1849-1856.
Scanning electron microscopy, scanning transmission electron microscopy and transmission electron microscopy are powerful tools in the analysis of crystalline materials. In combination with their associated analytical techniques, they roughly cover three length scales: the 'supra-nm' scale, the 'nm' scale and the 'sub-nm' scale, respectively. In this paper, the investigation of crystalline properties is presented, by means of 2D and 3D characterization examples. Techniques such as channeling contrast, electron backscatter diffraction, crystal orientation contrast on thin films and convergent beam electron diffraction are covered. Furthermore, time-efficient and site-specific focused ion beam and dual-beam sample preparation for any of the techniques above are introduced.
24.
Rho, B. S., H. U. Hong, et al. (2000). "Analysis of the intergranular cavitation of Nb-A286 alloy in high temperature low cycle fatigue using EBSD technique." Scripta Materialia 43(No. 2): 167-173.
25.
Richard, V., R. Chiron, et al. (2003). "Investigation of Dislocation Microstructures Formed in Heavily Deformed Metals Through the Combined Use of EBSD and TEM." Advanced Engineering Materials 5(3): 161-165.
New applications of the electron back scattering diffraction (EBSD) technique for studying dislocation microstructures are presented. Examples from copper and steel samples are given to illustrate the links between crystallographic measurements and dislocation micro structure. The purpose of combining transmission electron microscopy (TEM) and EBSD is to obtain quantitative information about the evolution and heterogeneity of the dislocation microstructure, and how it depends on the texture of the material. Materials: Cu, IF steel, and Al-1Mn.
26.
Rickards, J. (1987). "Crystallography Using the Diffraction of Proton-Induced X-Rays." Nuclear Instruments and Methods in Physics Research Section B 24-5(APR): 621-624.
27.
Rickerby, D. S. and A. Hendry (1986). "Strengthening of Nitrided Fe-Ti Alloys." Acta Metallurgica 34(10): 1911-1923.
28.
Rickert, T. J. (1996). Texture Development during Annealing of Ti- and Ti+Nb Stabilized 11% Cr Ferritic Stainless Steels. Eleventh International Conference on Textures of Materials, Xi'an, China, International Academic Publishers.
29.
Rinaldi, C., D. Robba, et al. (2003). Metallurgia Italiana 94(3): 41-47.
First stage rotating blades of gas turbines are now made with single crystal Nickel based superalloys. To reduce maintenance costs big efforts are presently devoted to find repair techniques for such materials, able to produce the same crystallographic orientation of the substrate in the repaired region (epitaxial growth). For such a purpose the laser cladding process can be used, if operating parameters are adjusted to obtain very high values of temperature gradient and low solidification velocities at the liquid-solid interface (conditions required by the epitaxial growth to occur). Starting from literature models an user-friendly software for PC was developed, able to drive the operator in the choice of operating conditions during the experimental trials of laser cladding repair. As input such a software requires data relative to the material and the experimental configuration of the laser cladding workstation. For any laser power value the outputs are the temperature distribution in the work-piece, the melt pool size and shape, thermal gradients and solidification velocity along the fusion line, but mainly the laser head speed and powder feeding values required to produce a fixed height. The alloy CMSX-4 was used for trials with an atomised self-similar powder. With a Nd: YAG laser (Lumonics 1 kW) epitaxial growths were produced, with a misorientation less than 13 deg on respect the substrate orientation. This result and the absence of small disoriented grains were evaluated by the electron backscattered diffraction technique (EBSD) in a scanning electron microscope with an eccentric specimen holder. Using the Nd:YAG laser an epitaxial growth was produced about 1.5 times higher than that obtained in literature with the same number of passes by a CO2 laser.
30.
Rioja, R. J. (1998). "Fabrication methods to manufacture isotropic Al-Li alloys and products for space and aerospace applications." Materials Science and Engineering A257(1): 100-107.
After a description of the evolution of Al-Li alloys, this paper first reviews the subject of anisotropy in mechanical properties of Al-Li wrought products. In plane, through thickness and axisymmetric flow anisotropies present in Al-Li wrought products are defined. The root causes for these anisotropies are discussed. Pros and cons arising from anisotropic products are then discussed in the context of designing and manufacturing for space and aerospace structures. Numerous attempts aimed to reduce anisotropy in rolled and extruded products are summarized. It is concluded that ‘isotropic’ Al-Li products can be manufactured via the selection of appropriate process, composition and processing parameters. © 1998 Elsevier Science S.A. All rights reserved.
31.
Ro, Y. J., S. R. Agnew, et al. (2004). "Uncertainty in the determination of fatigue crack facet crystallography." Scripta Materialia 52: 531-536.
The uncertainty of facet crystallography measured by stereology and electron backscattered diffraction is less than 3°, based on multiple measurements on an oriented Si single crystal and an Al–Li–Cu alloy fatigue crack. This provides a guideline for the characterization of physically meaningful differences in facet crystallography, which in turn guides damage mechanism assessment
32.
Robertson, I. M., T. C. Lee, et al. (1988). "Dynamic Studies of Deformation and Fracture at Grain-Boundaries." Journal de Physique I 49(NC-5): 677-680.
33.
Robins, A. C. and D. W. Smith (2003). Recent developments in automated sample preparation for FESEM. Microscopy of Semiconducting Materials Conference, Cambridge, UK, Inst. of Phys., Bristol, UK.
Standard analytical practice in the semiconductor industry depends on fast, efficient and reliable sample preparation prior to field emission SEM (FESEM). "In lens" imaging technology and orientation mapping demand sample surfaces free of physical damage and residual contamination. An integrated preparation tool has been developed that incorporates the functionality necessary for argon - oxygen plasma cleaning, ion beam etching (TBE), reactive ion beam etching (RlBE), reactive ion etching (RIE), and ion beam sputter coating (ISBC). Control, monitoring and sequential automation of the processes is accomplished through a novel combination of software and hardware. FESEM results for Al and Cu based microelectronic materials will be discussed, as well as electron backscatter diffraction results for bulk metals. Improvements in throughput and subsequent materials characterization will be demonstrated.
34.
Robson, J. D., B. J. McKay, et al. (2005). Modeling Dispersoid Precipitation and Re-crystallization in Scandium and Zirconium Containing Aluminum Alloys. 9th International Conference on Aluminium Alloys, Brisbane, Australia, Institute of Metals and Materials Australasia Ltd.
A model has been developed to predict the size, spacing, and distribution of the dispersoids in aluminum alloys containing zirconium and scandium. The model has been applied to predict the dispersoid pinning pressure in AA7050. The stored energy after deformation has been measured as a function of strain rate using EBSD This, in combination with the calculated pinning pressure, has been used to predict re-crystallization behavior during solution treatment. These predictions have been compared to experimental observations.
35.
Rodbell, K. P., J. L. Hurd, et al. (1996). "Blanket and local crystallographic texture determination in layered Al metallization." Materials Research Society Symposium Proceedings.
The effect of microstructure, including average grain size, grain size distribution, precipitate distribution and crystallographic texture, on the reliability of Al and Al-alloys is well documented. In this paper, the various X-ray methods available for measuring preferred orientation in blanket films are compared and contrasted in an effort to find the fastest most accurate method to acquire curves, and complete pole figures (fiber plots) were compared for four Ti/AlCu films having greatly different crystallographic texture components. The results show that it matters how texture is measured in a thin film; only pole figures (fiber plots) are unambiguous. In addition, the local texture in a series of stress-voided 0.48 mu m wide Ti/AlCuSi/TiN lines was measured using Backscattered Kikuchi Diffraction (BKD). Samples were chosen from two sets of identically prepared wafers (processed at different times) showing large differences in stress-voiding driven resistance versus time behavior. The more strongly textured (111) films had decreased stress-voiding lifetimes and tended to have smaller average grain sizes with slightly larger grain size distributions. This is in apparent contradiction with previous results in Al films, where improved stress-voiding and electromigration behavior were found in those films with the strongest (111) texture. (24 References).
36.
Rodbell, K. P., L. M. Gignac, et al. (1999). Crystallographic texture in 1G DRAM reactive ion etched vs. damascene Al-Cu lines. Twelfth International Conference on Textures of Materials (ICOTOM 12), McGill University, Montreal, Canada, NRC Research Press.
37.
Rodríguez, P. P., A. Ibarra, et al. (2004). "Influence of thermo-mechanical processing on the microstructure of Cu-based shape memory alloys produced by powder metallurgy." Materials Science and Engineering A 378(1-2): 232-237.
Cu–Al–Ni shape memory alloys processed by powder metallurgy show very good thermo-mechanical properties, much better than those found in alloys produced by conventional casting. In this paper, we present the microstructural characterisation of these powder metallurgy alloys in order to find the microscopic mechanisms, linked to the powder metallurgy processing method, which are indeed responsible of such good thermo-mechanical behaviour. Electron microscopy studies [scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM)] show that powder metallurgy processing creates a sub-grain structure characterised by the presence of low angle sub-boundaries. These sub-boundaries are found to be lying on {1 1 0} and {1 1 2} lattice planes and are composed by an arrangement of superdislocations. These sub-boundaries may improve ductility in two ways: acting as a sink of dislocations which promotes plastic deformation and decreasing stress concentration at grain boundaries. Moreover, since sub-boundaries act as weak obstacles for the movement of martensite plates, the improvement on ductility is accomplished by an adequate thermo-mechanical behaviour.
38.
Rodríguez-Reyes, M., M. I. Pech-Canul, et al. (2006). "Limiting the development of Al4C3 to prevent degradation of Al/SiCp composites processed by pressureless infiltration." Composites Science and Technology 66(7-8): 1056-1062.
The presence of Al4C3 in Al/SiC composites may activate degradation of the material by its interaction with water; even moisture may cause its environmental degradation. It has been demonstrated that incorporation of 6 vol% SiO2 powders into SiCp preforms before processing by pressureless infiltration prevents formation of Al4C3 Analysis by electron back-scattered diffraction confirms that regardless of its crystal structure (α-quartz or αcristobalite), SiO2 completely reacts to form MgAl2O4. The metal/ composite interface microstructure condition of the specimens processed under the most severe conditions (1100 f the lon C for 60 min), four months later confirms the effectiveness of the SiO2 powders.
39.
Rodriguez, P. P., J. San Juan, et al. (2003). Electron microscopy study of microtexture in Cu-Al-Ni shape memory alloys processed by powder metallurgy. International Conference on Martensitic Transformations, Espoo, Finland, EDP Sciences.
Cu-Al-Ni shape memory alloys processed by powder metallurgy show very good thermomechanical properties, being the mechanical behavior similar to the one observed in single crystals. In this paper we present the microstructural characterization of a sample elaborated by powder metallurgy in two different stages of the process: after being compacted by hot isostatic pressing (HIP) and after compaction and hot rolling, in order to find the microscopic mechanisms responsible of their mechanical behavior. The characterization has been carried out by means of scanning electron microscopy using backscattered electron imaging (SEM-BSE) and electron backscattered diffraction (EBSD), as well as transmission electron microscopy (TEM).
40.
Roelant, A. M., H. J. Wang, et al. (2005). An Investigation of TiC Particles Formed in an Amorphous Steel Matrix. Solid to Solid Phase Transformations in Inorganic Materials 2005, Phoenix, Arizona, USA, TMS.
Titanium carbide particles grown in an amorphous steel of composition Fe-15Cr-14Mo-2Er-15C-6B (wt. pct.) showed a bimodal distribution of particle types: smaller, faceted particles and larger dendritic-like particles. A transmission electron microscope investigation verified that the matrix is amorphous and that the smaller titanium carbide particles are faceted along low index planes. Electron backscattered diffraction characterized the micro-texture from these particles. The larger, dendritic -like particles have a random texture whereas the smaller, faceted particles have a medium fiber texture. The cause for this apparent texturing is unknown; however, this texturing does not lie along the casting axis of the rod.
41.
Rogers, K. A., K. P. Trumble, et al. (1994). "Role of Oxygen in Microstructure Development at Solid-State Diffusion-Bonded Cu/Alpha-Al2O3 Interfaces." Journal of the American Ceramic Society 77(8): 2036-2042.
42.
Rolland, P. and K. G. Dicks (2000). An Automated EBSD Acquisition and Processing System. Electron Backscatter Diffraction in Materials Science. A. J. Schwartz, M. Kumar and B. L. Adams. New York, Kluwer Academic/Plenum Publishers: 135-40.
43.
Rolland, P., K. G. Dicks, et al. (2002). High-Resolution EBSD Analysis of Deformed Material. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.
Crystal Orientation Mapping (COM) of fine grained or deformed material is highly dependent upon the microscope performance, i.e. spot size and control of aberrations. In addition, the Electron Backscatter Diffraction (EBSD) camera sensitivity dictates the miniumum probe current that can be used. Beyond the instrumental set up, the condition of the sample is critical. Recent work has shown that the smallest grain size that can be measured is ultimately limited by strain present at the grain boundary. The "effective resolution" of EBSD information is approximately 6nm using a Field Effect Gun Scanning Electron Microscope (FEG-SEM), and 30 nm using a Tungsten (W) filament SEM (W-SEM). However, when strain is present at the grain boundaries in the sample, the minimum grain size that can be determined is limited to ~50 nm and 150 nm respectively. Deformed material is often an aggregate of smaller grains forming the interior of larger grains, with varying degrees of strain being residual within the structure and concentrated at grain boundaries. Thus high spatial resolution is critical to achieve continuous coverage of EBSD data. In the case of deformed material, The FEG-SEM achieved the best continuity of crystal orientation information across deformed areas. Therefore, the FEG-SEM offers a considerable advantage compared to the W-SEM under these circumstances.
44.
Rollett, A. D., C.-C. Yang, et al. (1999). Extraction of Grain Boundary Energies from Triple Junction Geometry. Microscopy and Microanalysis, Portland, Oregon, Springer-Verlag.
45.
Rollett, A. D., M. Alvi, et al. (2005). Texture-Dependent Recrystallization in Aluminum 1050. 9th International Conference on Aluminium Alloys, Brisbane, Australia, Institute of Metals and Materials Australasia Ltd.
Recrystallization kinetics has been studied in hot rolled 1050 with the objective of understanding the local variation in the rate of recrystallization as a function of texture component. Automated electron back-scatter diffraction (EBSD, or OIM) has been used to quantify microstructures at various stages of recrystallization. Analysis of the grain orientation spread (GOS) was found to be the most effective method for partitioning EBSD maps into recrystallized and unrecrystallized regions. The cube component is weak in the as-deformed state but increases to between 25% and 40%, depending on annealing temperature. In order to verify that we understand the recrystallization process at the microstructural level, 3D Monte Carlo simulation of recrystallization has been undertaken using statistically reconstructed input microstructures to represent the deformed material.
46.
Romero, D., L. Martinez, et al. (1996). "Computer-Simulation of Grain-Boundary Spatial-Distribution in a 3-Dimensional Polycrystal with Cubic Structure." Acta Materialia 44(1): 391-402.
A close packed aggregate of Kelvin polyhedra is used to model the spatial distribution of different types of grain boundaries (GBs) in a three-dimensional polycrystal. Orthogonal matrices of rotation of a reference unit crystal are randomly generated and stochastically assigned to the volume units. The misorientation matrices of neighboring polyhedra are computed and low-angle and special misorientations are selected out of them. Finally, the positions of certain types of GBs in the volume under calculation determine what allows to fix the clusters of low-energy GBs. For various classifications of low-energy GBs, the frequency of cluster sizes in polycrystal is estimated.
47.
Ronay, M. and C. F. Aliotta (1980). "Hillock Formation in Lead Films by Grain-Boundary Sliding." Philosophical Magazine A 42(2): 161-184.
48.
Ros-Yáñez, T., Y. Houbaert, et al. (2001). "Characterization of TRIP-assisted multiphase steel surface topography by atomic force microscopy." Materials Characterization 47: 93-104.
Transformation-induced plasticity (TRIP)-assisted multiphase steels have a complicated microstructure consisting of different phases, mainly ferrite, retained austenite, bainite and martensite. Atomic force microscopy has been used for the phase identification and characterization of the phases in this kind of steel. A series of tests has been made on a C–Mn–Si and a C–Mn–Al TRIP-assisted steel after two different heat treatments: intercritical annealing followed by quench, and intercritical annealing followed by aging. After the aging process, the C–Mn–Al alloy was tempered in order to make metallographic observation easier, except the samples for mechanical testing, XRD or Mo¨ssbauer spectroscopy. It has been possible to identify the different phases and their topographic characteristics and to study their morphology using atomic force microscopy. The fine and complex microstructures of TRIP-assisted multiphase steels require improvements of the existing observation techniques, like electron backscattered diffraction and atomic force microscopy. Results of these techniques are presented.
49.
Rouag, N., H. Afer, et al. (2004). Consideration of Crystallographic Neighbourhood in Magnetic Sheets of Fe3%Si. Behaviour Prediction of Grain Growth from the Texture Function. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
The abnormal grain growth is related to the material texture, in the magnetic sheets Fe3%Si of HiB type, with AIN and MnS inhibitors. The onset of abnormal growth of Goss grains seems to be linked to the existence of a local favourable crystallographic neighbourhood. The grains which abnormally grow do not have a size greater than the average size in the matrix, their ability to grow in an abnormal way can be related to the local evolution around that considered grain, the whole effect of the matrix can hide the effect of matrix homogeneity.
50.
Roven, H. J., E. A. Starke, et al. (1990). "Effects of Texture on Delamination Behavior of a 8090-Type Al-Li Alloy at Cryogenic and Room Temperature." Scripta Metallurgica et Materialia 24(2): 421-426.
51.
Rowenhorst, D. J., A. Gupta, et al. (2006). "3D Crystallographic and Morphological Analysis of Coarse Martensite: Combining EBSD and Serial Sectioning." Scripta Materialia 55(1): 11-16.
This investigation combines EBSD analysis with serial sectioning to allow for direct, quantitative investigations into the 3D morphology and 3D crystallography of coarse martensite crystals formed in HSLA-100 steel. A method of 3D reconstruction is presented that creates an accurate representation of the microstructural features. It is then shown how the 3D crystallography can be represented both qualitatively within the 3D reconstructions, and quantitatively by constructing a Crystallographic Interface Normal Distribution (CIND). The CIND indicates that the coarse martensite crystals display four distinct facets, for which the specific crystallographic directions are determined for the three largest facets.
52.
Roy, R. K., S. Kar, et al. (2006). "A study of precipitation and recrystallization behaviour of aluminium alloy AA1235." Journal of Materials Science 41(4): 1039-1045.
The recrystallization behaviour of 92% cold rolled commercial pure aluminium has been studied. Annealing was done at different conditions to evaluate the effect of recrystallization temperature and time on the microstructure and texture of the alloy along with a study of subsequent precipitation. Variation of orientation between grains has been studied by the orientation imaging microscopy (OIM). During precipitation, cube component {001}<100> has dropped and rolling texture component {112} < 111 > has increased comparatively. Recrystallization texture is the combination of cube, rolling and random texture. However, during grain growth strong cube grains have formed. A significant number of dislocations are present during grain growth owing to the pinning effect of Al3Fe particles.
53.
Ruebenbauer, K. and U. D. Wdowik (2004). "Nucleogenic iron charge states in CoO studied by Mössbauer spectroscopy." Journal of Physics and Chemistry of Solids 65(11): 1785-1795.
Single crystal of CoO was doped by about 40-at. ppm of 57Co. Mössbauer spectra were measured vs. sample orientation, temperature and under reduced oxygen pressure, i.e. for a low cobalt vacancy concentration. Distinctly different iron charge states coexist till about 866 K. A mixed-valent state is observed above this temperature. It evolves gradually towards the Fe2+ state above 1255 K due to the decreasing mobility of holes, as compared to the mobility of the electrons. The ratio of the mobility of holes to the mobility of electrons increases with the increasing vacancy concentration, i.e. with the increasing oxygen pressure. Defects order into clusters below 866 K leaving behind almost perfect structure. A recoilless fraction exhibits some anharmonicity above 923 K.
54.
Ruggiero, M. A. and J. W. Rutter (1995). "Origin of Microstructure in 350 K Eutectic of Bi-in-Sn Ternary-System." Materials Science and Technology 11(2): 136-142.
55.
Russell, J. D., D. C. Halls, et al. (1997). "The Relationship Between Crystal Misorientation and Conductive Mode Contrast of Grain-Boundaries in Additive-Free Zinc-Oxide." Journal of Materials Science 32(17): 4585-4589.
56.
Rutter, N. A. and B. A. Glowacki (2001). "Modelling of Orientation Relations in 2-D Percolative Systems of Buffered Metallic Substrates for Coated Conductors." IEEE Transactions On Applied Superconductivity 11(1): 2730-2733.
57.
Ryde, L., B. Hutchinson, et al. (2004). Grain Boundaries with High Misorientation and Low Mobility. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
Island grains have been studied in iron samples that had been treated by critical-strain-annealing and in commercial silicon iron alloy sheets after incomplete secondary recrystallisation. Such islands remain behind because their boundaries have such a low mobility that the grains cannot shrink away in the time available during annealing. Misorientations of these islands in relation to the grains surrounding them were measured using EBSD Similar results were observed in both materials. A small number of low angle boundaries were found and also many twin boundaries. The most remarkable observation, however, was the presence of many general high angle boundaries that did not correspond to any evident coincidence relation.
58.
Ryoo, H. S., S. H. Yu, et al. (2002). Monte Carlo Simulation of Grain Growth in Zr Processed by ECAP. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.
Grain boundary character distribution of commercially pure Zr (Zr702) was studied by experiment in conjunction with the Monte Carlo computer simulation. With the application of equal channel angular pressing (ECAP) the grain size was efficiently reduced to 310nm. A strong basal texture developed in the as-deformed specimen with a microstructure consisting of mostly high angle grain boundaries. The crystal texture and the grain boundary characteristics were insensitive to the subsequent heat treatment at 800°C. This phenomenon, confirmed by experiment and by the computer simulation as well, was attributed to the high mobility of mostly high angle grain boundaries formed during ECAP and subsequent recrystallization.
58 records found
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