ICAMS / Interdisciplinary Centre for Advanced Materials Simulation


Observation and initial modeling of deformation microstructures in FCC and BCC mesocrystals

Date: 22.06.2009
Place: Institute of Mechanics, TU Dortmund, Germany

Bob Svendsen, Universität Dortmund, Dortmund, Germany

As has been documented by many experimental investigations, sustained loading of polycrystalline metals results in deformation localization, deformation heterogeneity and deformation / dislocation-based microstructural development. This is particularly true at grain boundaries and triple-junctions in such systems, and leads to complex local stress- eld variations driving further deformation-based microstructural development. Among other things, such processes a ect the local lattice orientation and its distribution within grains and across their boundaries in the system. In the last few years, a number of studies (e.g. 1,2) have shown that experimental methods such as electron back-scattering di raction (EBSD) and orientation imaging microscopy (OIM) can be used to determine crystal lattice orientation distributions on the sample surface as a function of position in the sample with resolution of 1 m or better. Using these and related methods, one can determine in particular orientation gradients and relate these to lattice curvature. In turn, this curvature can be related in a model-dependent fashion to the density of geometrically-necessary dislocations (GNDs). The purpose of the current work is the experimental characterization and initial model- ing of the material and structural behavior in large-grained thin FCC and BCC sheet metal \mesocrystal" specimens subject to quasi-static loading. To this end, the development of deformation microstructure in such specimens has been characterized experimentally with the help of EBSD and other methods. On the modeling side, both standard crystal plas- ticity and its extension (e.g. 3) to include the e ects of GNDs on the material and in particular on the hardening behaviour have been utilized and are being further developed. Modeling details and initial simulation results will be discussed.

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