Influence of twinning deformation and lattice rotation on strength differential effect in polycrystalline pure magnesium with rolling texture

The microstructural mechanism of the strength differential (SD) effect in polycrystalline pure magnesium with rolling texture is numerically investigated by rate-dependent crystal plasticity finite element analysis. The present analysis method considers basal slip, prismatic slip, first-order pyramidal slip, and second-order pyramidal slip, as well as deformation twinning due to c-axis tension. Critical resolved shear stresses (CRSS) of single crystal pure magnesium reported in the literatures are used for the material parameters in the analysis. The SD effect in a numerically generated material, which has a strong texture typical of rolled magnesium, is examined by simulating tensile and compressive tests. The results show a significant SD effect due to deformation twinning. The results of simulations that do not take deformation twinning into account, however, still show a non-negligible SD effect. This persistent SD effect, which has no relation to the twinning, is explained in terms of lattice rotation and different CRSS on different slip systems.