Dislocation pattern formation in the course of plastic deformation

Abstract

The self-consistent evolution of a two-dimensional screw dislocation ensemble is investigated in plastically deformed crystal. A generalized isotropical multicomponent model for dislocation dynamics is proposed. It is found that the intense relaxation process of the excess Burgers vector of the two-dimensional screw dislocat ensemble results in the establishment of an effective diffusion regime for average density ρ,(r,t) evolution. In a two-component system this gives rise to mutual component interdiffusion, playing an important role in the nonlinear evolution stage. Two types of spatial structures are found to emerge in the course of plastic deformation: i) a one-dimensional structure, which is established due to rivalry between unstable modes and results in the emergence of reorientation bands in the crystal; ii) a two-dimensional structure, which is established due tocooperation of the modes and is responsible for the hexagonal cell formation in the crystal. It is shown that for a sufficiently low strain level a hexagonal cellular structure is preferable.