Ultra strength-ductility synergy in the Mg-Al-Zn alloy via densely dispersed multi-scale {1012‾} tension twins

Enhancing the strength and ductility of widely used Mg–Al–Zn alloys is an urgent requirement for Mg alloy load-bearing components. Ultra-fine grains and a large amount of β-Mg 17 Al 12 precipitates improve their strength but reduce ductility. This work developed a commercial AZ80 alloy with the ultimate tensile strength (UTS) of 512 MPa and elongation to failure (EF) of 19.8% using a combination of extrusion and multi-directional forging processes, which has superior strength-ductility synergy among the reported AZ80 alloys and reaches the level of wrought Mg-RE alloys. The excellent mechanical properties are attributed to the formation of densely dispersed multi-scale {10 12 ‾ } tension twins. The introduction of ultra-fine {10 12 ‾ } twins reduces the mean free path of dislocations leading to a faster dislocation accumulation, which improves the work hardening ability of the alloy. This work provides a new insight into the development of low-cost Mg alloy forging billets with high strength and ductility.