Dislocation-crystal plasticity simulation on formation process of ultrafine-grains based on geometrically necessary crystal defects

Ultrafine-grains (UFG) are induced by warm or cold-rolling process under severe plastic deformation. A transition of microscopic structure of a metal caused by behaviors of dislocations is closely connected with a macroscopic deformation. The information of dislocation field and deformation field is desirable to be coupled in the case of simulation of UFG formation. Profiles of formation process of UFG, e.g., aspects of subdivision and induced grain sizes, are expected to be numerically predicted. In this paper, a numerical method for estimating generation of subdivisions is proposed, and also the induced grain size is introduced into a strain rate sensivity model as an argument. A dislocation-crystal plasticity FE simulation based on the geometrically necessary crystal defects proposed in the previous paper and on the above model is carried out for large deformation of an FCC polycrystal under severe compression plane strain. Distributions of crystal defects and crystal orientations in a specimen are visualized and the influence of strain on separation of grains and one of strain rate sensitivity on refinement of grains under cold-rolling process are discussed in detail.