A novel dynamic extrusion for microstructure tailoring and evading strength-ductility trade-off in AZ31 magnesium alloy

Abstract This study demonstrates that dynamic extrusion is a promising method for improving both strength and ductility in magnesium (Mg) alloy. The dynamic extrusion process introduces numerous {10-12} extension twins and high-density dislocation structures in the fine-grained AZ31 Mg alloy at high strain rate (~105 s-1) and room temperature. After annealing, we note that the high-density twins can effectively enhance the strain hardening and strength due to that twin boundary is inherently resistant to dislocation motion. Remarkably, the excellent ductility has been achieved because of high density deformation twins promote more dislocation to nucleate form twin boundaries, and offer more slip systems for dislocation motion. Our findings suggest dynamic extrusion increases the twin density of the initial microstructure, thereby simultaneously increasing both of the strength and ductility in Mg alloy. Ultimately, our work develops a novel strategy or technique to properly tailor microstructure to achieve a substantial improvement of mechanical properties in Mg alloys.