A phase-field model of twinning and detwinning coupled with dislocation-based crystal plasticity for HCP metals

In this study, a phase-field model describing both twinning and detwinning that is coupled with a dislocation-based crystal plasticity model is constructed for HCP metals, particularly for magnesium. The driving force of twinning is assumed to be resolved shear stress acting on the twin system. The plastic anisotropy of dislocation mobility in an HCP crystal is described via the dislocation mean free path model, which is incorporated into the hardening law. These models are coupled through an order parameter and stress. Using the present model, several FE analyses on single-crystal magnesium are carried out. The obtained results show that the nominal stress-strain response, twinning and detwinning behavior and the consistent value of twin shear around twins are reproduced by this model. In addition, from the results of tensile simulation of a specimen including a number of twin nuclei, twin nucleation is suggested to occur so as not to increase the mechanical energy by the accumulation of elastic strain and dislocation.