High strength and ductility in a rare-earth free magnesium alloy processed by rotary swaging and flash annealing
Yunhao Fan, Yizhuang Li, Hui Guo, Gaoming Zhu, Boyu Liu, Hao Wang, Hao Zhou, Yuling Xu, Xiaoqin Zeng, Leyun Wang
Abstract
Magnesium (Mg) is the lightest structural metal. It is promising for aerospace applications if its mechanical properties can be improved at a reasonable cost, without using expensive alloying elements or time-consuming processing routes. Here, we develop a rare-earth free Mg-Al-Ca alloy, processed through rotary swaging followed by flash annealing. The resulting alloy exhibits superior strength and ductility, surpassing nearly all reported rare-earth free magnesium alloys. Nanosized Al-Ca precipitates and clusters, formed largely during rotary swaging and flash annealing, significantly strengthen the alloy. Deformation twinning is suppressed, necessitating the formation of more <c + a> dislocations to accommodate the severe plastic strain induced by rotary swaging. These <c + a> dislocations are retained during flash annealing due to the high climb energy barrier and pinning by those nanosized Al-Ca precipitates and clusters. This retention of <c + a> dislocations contributes to high ductility and provides forest hardening, further increasing strength. This study offers a simple strategy for designing and fabricating high-performance magnesium alloys. Retarded dislocation activity in magnesium alloys typically limits ductility. Here, high strength and ductility are achieved in a rotary swaged and flash annealed rare earth-free magnesium alloy, attributed to nanosized Al-Ca precipitates and dislocation activation with limited twinning.