Deformation behaviour of 18R long-period stacking ordered structure in an Mg-Zn-Y alloy under shock loading

The deformation microstructure of an interdendritic18 R long-period stacking ordered (LPSO) phase in an Mg-Zn-Y alloy subjected to shock loading was investigated by transmission electron microscopy. It was found that kink banding, the key deformation mode of LPSO phases under quasi-static loading, is suppressed by shock loading. Instead, second-order pyramidal slip by <c+a> dislocations, which has not been observed in LPSO before, contributes to the plastic deformation of LPSO, in addition to the <a> dislocations. The rate-dependent deformation modes of LPSO have an important implication in understanding the mechanical behaviour of LPSO strengthened Mg alloys under extreme loading conditions.