Investigation on the microstructure and mechanical properties of a cast Mg-6Zn-5Al-4RE alloy

Mg-6Zn-5Al-4RE (RE = Mischmetal, mass%) alloy was prepared by metal mould casting method. The microstructure and mechanical properties of the as-cast and heat-treated alloys were investigated. The results show that the phase compositions of the as-cast state alloy are supersaturated solid solution α-Mg, lamellar β-Al12Mg17, polygonal Al3RE and cluster Al2REZn2 phases. The mechanical properties, especially the ultimate tensile strength and elongation of the alloy were significantly improved by the heat treatment. Fracture surface of tensile specimens was analyzed by optical microscope and scanning electron microscope.