Strain hardening at large strains as predicted by dislocation based polycrystal plasticity model

A recent strain hardening model for late deformation stages (Estrin, Y, Toth, L.S., Molinari, A., and Brechet, Y., Acta Materialia, 1998, "A dislocation-based model for all hardening stages in large strain deformation," Vol. 46, pp. 5509-5522) it-as generalized for the 3D case and for arbitrary strain paths. The model is based on a cellular dislocation arrangement in which a single- phase material is considered as a composite of a hard skeleton of cell walls and soft cell interiors. An important point in the approach is the evolution of the volume fraction of the cell walls which decreases with the deformation and gives rise to a plateau-like behavior (Stage IV) followed by a drop-off (Stage V) of the strain hardening rate observed at large strains. The hardening model was implemented into the viscoplastic self-consistent polycrystal model to predict hardening curves corresponding to different proportional loading paths. The calculated curves were evaluated to elucidate the path dependence of hardening.