Microstructure of water quenched as-cast MgY5Mn1Sc0.3 magnesium alloy and its microsructural evolution after solid solution at 520 ℃with different holding times were observed by OP（optical microscope）

SEM and XRD. The results show that the as-cast microstructure is composed of coarse grain

where amounts of plait-like twins crystal and linear-array particle phase occur

and the absence of dendrite and eutectic phase within grain and boundary is observed

meanwhile the Y element is severely segregated to enrich the second particle phase. After solid solution treatment

there occurs the microstructure evolution and recrystallization evolving spheroidization of grain

dissolution and congregation of dispersive phase

and the transformation of the grain. The effects of heat treatment on the experimental alloy were investigated by measuring the hardness HV100.