Effects of Sn content on the microstructure and mechanical properties of Mg–7Zn–5Al based alloys

The microstructures and tensile properties of the as-cast and heat treated Mg–7Zn–5Al based alloys with 1–6 wt.% Sn addition were studied. The results show that all the Sn-containing alloys consist of α-Mg, τ-Mg32(Al, Zn)49, β-Mg17Al12 and Mg2Sn phases. The addition of Sn refines the τ-Mg32(Al, Zn)49 phase and suppresses the formation of network-shaped phase. Tensile tests indicate that the Sn-containing alloys exhibit excellent heat resistance, and the yield strength increases with increasing the Sn content. The ageing treatment can obviously improve the tensile strength of the studied alloy, while the aged Mg–7Zn–5Al–2Sn alloy has optimal mechanical properties.