Two-internal variable thermodynamics modelling of severe plastic deformation: dislocation and flow stress evolutions

Abstract

Two-internal variable thermodynamics model is presented to investigate the evolution of microstructure and flow stress during severe plastic deformation. Previous studies have shown that due to heterogeneous distribution of dislocations during severe plastic deformation, the use of multivariable models is needed. In this regard, a two-internal variable model is presented. In the present paper, the dislocation densities in the subgrain boundaries and interiors are considered as internal variables. The model uses general laws of thermodynamics and describes the evolution of the dislocation densities on the basis of parameters such as the self-diffusion activation energy and the stacking fault energy. The model predicts the dislocation density, subgrain size and strength. To verify the model, the achieved results are compared with the experimental data.