Modelling the role of slips and twins in magnesium alloys under cyclic shear

Magnesium alloys under cyclic shear show different deformation behaviour from that under cyclic tension–compression, for example, symmetry vs. asymmetry of stress–strain curves. Using the Twinning–DeTwinning (TDT) model, we studied the role of different deformation mechanisms, slip systems, twinning and detwinning, in shear deformation behaviour of magnesium alloys. The results indicate that the nearly symmetrical shear stress-shear strain curve unlike the asymmetrical stress–strain curve under cyclic tension–compression is ascribed to the dominated prismatic slips and the simultaneous activation of deformation twinning and detwinning under reverse shear. The typical shear texture observed in experiments is ascribed to the activation of extension twin that induces the extension strain along normal direction of the shear plane under simple shear.