Aging Behavior of Mg-Y-Zr and Mg-Nd-Zr Cast Alloys

Aging behavior of Mg-3.6Y-0.5Zr and Mg-2.7Nd-0.5Zr alloys was investigated by microhardness measurement and transmission electron microscopy. In the case of Mg-Y-Zr alloy, the presence of β″ phase, a major strengthener, having base centered orthorhombic structure with its lattice constants of aβ″=0.64 nm, bβ″=2.22 nm, and cβ″=0.52 nm was identified. In the case of Mg-Nd-Zr alloy aged at 250℃, the presence of β″ and β′ phases was identified. The crystal structure of β″ phase was found to be DO19 and its orientation relationships with Mg matrix were 0001] β″//0001]Mg and 01 0] β″//01 0]Mg. The β′ phase had face centered cubic structure and its orientation relationships with Mg matrix were 011] β′//0001]Mg and 1 ]β′// 110]Mg. The Mg-2.7Nd-0.5Zr alloy showed higher hardness compared with Mg-3.6Y-0.5Zr alloy.