Evolution of dislocation cell structures in plastically deformed metals

We use a recently developed microstructure evolution model with stochastic dynamics to study the evolution of ordered dislocation patterns. Dislocations are described as groups arranged into arrays, with an initially random distribution of orientations, moving in an isotropic viscous medium. Stochastic displacements of dislocation walls describe the rearrangement of small groups of dislocations to form minimum-dissipation cells structures while lowering the overall misorientation. The result of large mechanical deformation, as could occur in cold-working, is simulated by introducing a preferential direction along which misorientation gradients of various kind are superimposed. The simulations show the emergence of ordered microstructure patterns, with high-density dislocation boundaries running perpendicular to the initial gradient, and a low-density cellular band structure in between. The results are compared to experimental data in heavily cold-worked metals.