Multiscale crystal plasticity modeling based on geometrically necessary crystal defects and simulation on fine-graining for polycrystal

It is important to develop a simulation model reproducing a formation process of ultrafine-grained metals under severe plastic deformation in order to obtain high-strength materials. In this study, we define two kinds of densities of the geometrically necessary (GN) crystal defects suitable for a crystal plasticity theory, i.e., densities of GN dislocation and GN incompatibility corresponding to isolated dislocation and dislocation pairs, respectively. We introduce these dislocation densities with dynamic recovery effect into the hardening law of a single crystal. Moreover, a multiscale crystal plasticity FE simulation is carried out for an FCC polycrystal under severe strain condition. It is computationally attempted to predict the formation of fine-grains and to visualize distributions of dislocation densities and crystal orientations in a specimen. We discuss about a generation of subdivision with large angle boundaries separated by GNBs and refinement of deformation-induced grains.