A superplastic bimodal grain-structured Mg–9Al–1Zn alloy processed by short-process hard-plate rolling

Superplasticity is usually obtained in uniform fine-grained materials processed by severe plastic deformation or multi-pass controlled rolling. However, we highlight a superplastic bimodal grain-structured Mg–9Al–1Zn (AZ91) alloy processed by hard-plate rolling (HPR). The present bimodal grain-structured alloy exhibits a notable elongation of ∼580% upon tension at 573 K and 1 × 10−3 s−1. The superplasticity is accommodated by the cooperative process of continuous dynamic recrystallization (CDRX) within coarse grains and grain boundary sliding (GBS) in fine-grained regions at early tension stage, followed by GBS controlled by grain boundary (GB) self-diffusion being the dominant deformation mode at late stage.