Facilitating single-pass rolling on as-cast AZ91 alloy by rotary-die equal channel angular pressing

To address the issues of poor plasticity at room temperature, low efficiency and high processing costs associated with conventional rolling on Mg alloys, rotary-die equal channel angular pressing (RD-ECAP) technology was applied to an as-cast AZ91 alloy to facilitate single-pass rolling. The effect of single-pass rolling on the as-cast AZ91 alloy and ECAP-processed alloy was comparatively studied by evaluating the microstructure and mechanical properties. Results indicated that, the microstructure of the rolled AZ91 alloys without RD-ECAP pretreatment exhibited coarse microstructure with significant twinning. The mechanical properties were suboptimal, particularly in terms of ductility, which was notably low. Edge cracks were prevalent, indicating poor plasticity of the as-cast alloy. After RD-ECAP pretreatment, the microstructure of the rolled alloy was significantly refined and homogenized. The mechanical properties were markedly enhanced, with both strength and ductility showing substantial improvements. Edge cracks were almost entirely eliminated, suggesting improved plasticity in the RD-ECAP pretreated alloys. This enhancement in plasticity was attributed to the refined microstructure and non-basal texture generated by RD-ECAP. The improvements in strength and ductility were also facilitated by RD-ECAP pretreatment, which promoted microstructure refinement and texture softening in the subsequently rolled alloys.