Papers by Keyword: Microdiffraction

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Authors: Ravi C. Gundakaram, Sai Pramod Pemmasani
Abstract: The behaviour of a coating is directly related to its microstructure as well as the crystal structure and composition of different phases that are formed in the deposition process. A comprehensive study of the microstructure and local phase assembly in coatings would help in arriving at structure-property correlations that can help understand the coating behaviour. SEM-based diffraction techniques provide a simple method for obtaining local crystallographic information without the need for complex synchrotron sources. In this study, we present a method for characterization of coatings using SEM-based microdiffraction which involves the combined use of the EDS and EBSD capabilities, citing a Ti-Al-Cr-N multilayer coating as an example. The different layers in the coating were observed and the electron beam focused in each region to first obtain Energy Dispersive Spectra and electron backscatter patterns (EBSPs). The elemental constituents were identified from EDS maps and used to shortlist the possible phases present. The diffraction pattern for each possible phase was then calculated and the EBSPs of the observed and calculated patterns were compared for the closest match. The identified phase was then used as an input to set up EBSD scans across the coating. A qualitative picture of the compositional variation in multilayer coatings was obtained that could help in arriving at the exact stoichiometry of the different layers. Hence, SEM-based microdiffraction allows identification of local crystallographic phases and composition, permitting detailed microstructural studies that would find special application in the study of coatings.
Authors: Bob B. He, Kingsley L. Smith, Uwe Preckwinkel, Willard schultz
Authors: H.D. Joo, J.S. Kim, C.W. Bark, J.Y. Kim, Yang Mo Koo, Nobumichi Tamura
Abstract: In-situ measurement of local orientation and strain Has Been carried out for a copperpolycrystals under a uniaxial loading using a synchrotron x-ray microdiffraction method at the Advanced Light Source. The heterogeneities of deformation-induced microstructure within single grains were observed. There were differences in the selection of simultaneously acting slip systems among neighboring volume elements within a grain.
Authors: Brent L. Adams, David J. Dingley, Karsten Kunze, Stuart I. Wright
Authors: Thomas Wroblewski
Abstract: A novel X-ray diffraction method, allowing the position resolved imaging of a polycrystalline specimen using the diffracted radiation, was applied for in situ investigation of recrystallization of cold-rolled copper. A large area of the specimen could be observed simultaneously, yielding information about nucleation and growth of many individual crystallites. The recrystallization process showed a stochastic behavior which can be described by the model of self-organized criticality.
Authors: Olivier Castelnau, Thierry Chauveau, M. Drakopoulos, A.A. Snigirev, I. Snigireva, C. Schroer, Tamás Ungár
Authors: Olivier Castelnau, Tamás Ungár, M. Drakopoulos, A.A. Snigirev, I. Snigireva, C. Schroer, Thierry Chauveau, Brigitte Bacroix
Authors: Stuart I. Wright, A.J. Beaudoin, George T. Gray III
Authors: J.D. Budai, W. Yang, B.C. Larson, J.Z. Tischler, W. Liu, Hasso Weiland, Gene E. Ice
Abstract: A new technique for investigating 3D grain growth in polycrystalline materials using white x-ray microdiffraction with micron point-to-point spatial resolution is presented. This technique utilizes focused polychromatic x-rays at the Advanced Photon Source, differential aperture depth-profiling, CCD measurements, and automated analysis of spatially-resolved Laue patterns to measure local lattice structure and orientation. 3D thermal grain growth studies of hotrolled aluminum have been initiated to demonstrate the capabilities of this method. Complete 3D grain orientation maps were obtained from a hot-rolled aluminum polycrystal. The sample was then annealed to induce grain growth, cooled to room temperature, and re-mapped to measure the thermal migration of all grain boundaries within the same volume region. Initial observations reveal significant grain growth above 360°C, involving movement of both low- and high-angle boundaries. Systematic measurements have been obtained of the as-rolled grain structure and of the microstructural evolution after annealing at successively higher temperatures. Small second-phase precipitates have been identified. Such measurements will provide the detailed 3D experimental link needed for testing theories and computer models of 3D grain growth in bulk materials.
Authors: Olivier Castelnau, Philippe Goudeau, G. Geandier, Nobumichi Tamura, Jean Luc Béchade, M. Bornert, D. Caldemaison
Abstract: The overall plastic behavior of polycrystalline materials strongly depends on the microstructure and on the local rheology of individual grains. The characterization of the strain and stress heterogeneities within the specimen, which result from the intergranular mechanical interactions, is of particular interest since they largely control the microstructure evolutions such as texture development, work-hardening, damage, recrystallization, etc. The influence of microstructure on the effective behavior can be addressed by physical-based predictive models (homogenization schemes) based either on full-field or on mean-field approaches. But these models require the knowledge of the grain behavior, which in turn must be determined on the real specimen under investigation. The microextensometry technique allows the determination of the surface total (i.e. plastic + elastic) strain field with a micrometric spatial resolution. On the other hand, the white beam X-ray microdiffraction technique developed recently at the Advanced Light Source enables the determination of the elastic strain with the same spatial resolution. For polycrystalline materials with grain size of about 10 micrometers, a complete intragranular mechanical characterization can thus be performed by coupling these two techniques. The very first results obtained on plastically deformed copper and zirconium specimens are presented.
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