Strength–ductility combination of fine-grained magnesium alloy with high deformation twin density

The objective of present study is to determine the effects of grain size and deformation twin density on mechanical behaviors linked to microstructure evolution of AZ31 magnesium (Mg) alloy. The AZ31 Mg alloy was processed by warm sever plastic deformation method and followed by dynamic compression (strain rate ∼ 1 × 103 s−1, plastic strain ∼ 10%). Uniaxial tensile experiments at room temperature have revealed that AZ31 Mg alloy is exhibited enhanced strength with grain refinement and high deformation twin density. The improved strength of AZ31 Mg alloy is attributed to the hindering effect of increasing grain boundaries (GBs) and twin boundaries (TBs) on dislocation motion, thereby making plastic deformation more difficult. As a result, the large reduction in ductility has been found for fine grained AZ31 Mg alloy (grain size is about 2–3 μm). But with increasing deformation twin density after dynamic compression (especially in fine grained samples), the obvious ductility enhancement has been found in both coarse grained and fine grained AZ31 Mg alloy. With mechanical behaviors properly described, both strength and ductility can be simultaneously achieved in fine grained and high twin density AZ31 Mg alloy. •Dynamic compression and ECAP were used to microstructure tailoring.•Dynamic plastic deformation can effectively increase the twin sensitivity in Mg alloy.•Grain refinement and pre-twinning can improve the both strength and ductility in Mg alloy.•High twin density shows better improvement in ductility of Mg alloy.