Plastic strain accommodation and crack initiation in a randomly-oriented Mg–8Y–1Zr magnesium alloy during accumulated tensile deformation

The deformation mechanisms in Mg–8Y–1Zr alloy during tensile deformation were investigated based on the quasi-in-situ EBSD combined with VPSC simulation. The results showed that pyramidal slip exhibits a high activity, but that of {10–12}<10–11> extension twinning is low as tensile stress/strain increases. By tensile stress, the deformation modes are activated in the sequence of basal slip, prismatic slip， {10–12} extension twinning and pyramidal slip. The multiple slips occur due to the narrowing of the difference in their CRSSs, which is favorable for plastic strain accommodation in and between grains. Cracks initiate on grain boundaries, and tend to be perpendicular to the tensile stress. This is the reason why the fracture surface shows a morphology of an inter-granular and inner-granular mixed character. The crack initiation is related to the local shear stress along a grain boundary and the grain boundary orientation with respect to the tensile stress direction.