Effects of RE element Y on the microstructure of ZM5 Mg alloy

The effects of different Y contents on microstructure of ZM5 Mg alloy were investigated by optical microscope and SEM and EPA. It was found that 2% Y addition can obviously improve the microstructure of the ZM5 Mg alloy. X ray diffusion and OM observation indicated as-cast microstructure of the alloy consists of α-Mg phase and net-like (β-Mg12Al17 phase in boundary, in which solid solution treated β-Mg12Al17 phase was dispersed in the matrix, in turn, microstructure of ZM5 alloy containing Re element Y consists of a phase, β-Mg12Al17 phase and particle MgY phase. Solid solution treated alloy consists of MgY phase and precipitated Al12Y phase. SEM showed that ZM5 Mg alloy possesses the features of cleavage fracture while ZM5 Mg alloy containing Y has mixed fracture morphology of quasi-cleavage fracture and boundary fracture. The reason is that enhancing phase MgY and dispersely precipitated phase transform the fracture morphology.