Investigation on position of kink band formation in single crystal of Mg-based LPSO phase using dislocation-based crystal plasticity simulation

Two-dimensional FE simulations on prediction of position of kink band formation for a single crystal of a Mg-based LPSO phase are performed using a dislocation-based crystal plasticity model. We take account of activities of basal, prismatic and 2nd-pyramidal slip systems and assume that the LPSO phase is simply composed of HCP lattices for simplicity. However, a HCP crystal such as Mg and the LPSO crystal are distinguished by magnitude of critical resolved shear stresses of the slip systems and elimination of deformation twins. In addition, to express crystal defects in the kink band within the framework of continuum mechanics, GN dislocation density, SS dislocation density and GN incompatibility (disclination density) are incorporated into the hardening rule. We carry out the FE simulation. First, we assign initial dislocation density homogeneously to a specimen used in the simulation. The result shows that a kink band is formed in the center of the specimen and distributions of densities of isolated dislocations, dislocation pairs and disclinations are appropriately expressed by the present models of crystal defects. Next, introducing a heterogeneity into the distribution of the initial dislocation density, we investigate the effects on kink deformation in terms of total elastic strain energy. As a result, the position of a kink band formation changes so that the energy is structurally minimized.