Papers by Keyword: Texture Effect

Abstract: In the last ten years of ongoing research in the modeling of polycrystalline ferroelectric ceramics a myriad of analytical and numerical implementations have emerged to predict and support the engineering of ferroelectrics in both its single-crystal and polycrystalline forms. Traditional atomistic approaches capture the intrinsic behaviors, and have led to great improvements in the chemistries of these systems. Similarly, macroscopic engineering approaches have focused on the development of phenomenological descriptions that capture the empirical static and time-independent behavior. At the interface of these two apparently divorced approaches, thermodynamic-based microstructural evolution descriptions inspired in phase field models have risen as the necessary link between the atomic and macroscopic levels. This new and emerging methodology starts from the predicted behaviors given by their atomic counter-parts, and resolves the effects of grain boundaries, and de-convolves the grain-grain mesoscopic interactions. Much of the future of ferroelectrics lies in the delivery of improved chemistries and microstructures, and on bridging the understanding currently existing atomistic and continuum descriptions. Overall, it is expected that current and emerging technological challenges will be the driving force to minimize ferroelectric fatigue and realize lead-free materials with performances close to currently existing (lead containing) ones. Moreover, it is expected that while an accurate understanding of the intrinsic properties of materials are key to define improved ferroelectric solids, it will be the detailed understanding of the extrinsic response of ferroelectric materials, in both bulk and thin film form, that will take these materials to reach the highest performances possible.

Abstract: The deformation behaviour of the highly textured Mg-base wrought alloy AZ31 subjected to tensile and compressive elasto-plastic loading was characterized by means of synchrotron radiation. In former publications it was shown that there exists an asymmetry in the deformation behaviour of the investigated alloy, which can be related to the deformation mechanism of the hexagonal structure due to the crystallographic texture relative to the loading direction. A local X-ray stress analysis was carried out on highly textured metal sheets for different {hkil}- planes of the hexagonal crystal structure. The load transfer was investigated within in-situ loading experiments in order to account for suitable XEC´s, thus ensuring accurate stress evaluations. An X-ray imaging method was applied in order to provide bending stress distributions with a high local resolution using synchrotron radiation (beamline G3, Hasylab (DESY)). Stress analyses were carried out on the side face of a bending bar being subjected to elasto-plastic bending up to total strains in the outer layers of approximately 2%. It is distinguished between loading stress distributions measured in in-situ loading experiments as well as residual stress distributions monitored after unloading of elasto-plastically bended bars. Furthermore the loading direction was alternated, in order to investigate the effect of the twin formation as well as the reversibility of the twinning on the results of X-ray stress analysis.