Evolution of microstructure and mechanical properties of ZK60 magnesium alloy processed by asymmetric lowered-temperature rolling

Asymmetric lowered-temperature rolling was applied to the fabrication of fine-grained ZK60 magnesium alloy sheet with weak basal texture along the rolling direction (RD). The results showed that multi-pass lowered- temperature rolling could significantly improve the microstructure homogeneity and refine the grain size. Meanwhile, a fiber texture along the transverse direction (TD) gradually developed during rolling process. Importantly, the shear deformation along the RD made the c-axis of basal plane rotate to the RD, weakening the basal texture along this direction. Influenced by such microstructure variation, the yield strength along the TD continuously increased due to the successive grain refinement and the increased activation of prismatic slips, whereas the uniform elongation decreased owing to the decline of strain hardening ability. In contrast, the continuous weakening of basal texture along the RD increased the activation of soft basal slips, greatly offsetting the strengthening effect contributed by grain refinement and thereby causing the slight decrease of yield strength.