Enhancement of ductility in low temperature regimes via detwinning in Mg alloys

Effect of pre-induced {10$\overline{1}$2} twin boundaries on tensile response at low temperatures of 77 K ∼ 293 K is examined in the Mg-Al-Zn alloys. Irrespective of temperatures, the specimens containing twins exhibit lower yield strength than those of specimens without twins, due to detwinning behavior. However, the ductility and absorption properties are significantly enhanced by the presence of these twins. This is owing to existences of dislocations with 〈c〉 component, which are generated by dislocation transformation through twin boundary migration. The pre-induced twin boundaries with 〈c〉 and/or 〈c + a〉 dislocations play a role in relaxation of strain accumulation as well as compensation of slip systems; thus, leading to retardation of localized necking. The twin boundaries with control of interfacial structures break a negative notion that twins are harmful for mechanical properties relating to ductility. This strategy can open a door for new microstructural design of Mg alloys.