Microstructural characterizations and mechanical properties of Mg-8Sn-1Al-1Zn-xCu alloys

Microstructural characterization and mechanical properties of as-cast Mg-8Sn-1Al-1Zn-xCu (x=0wt%, 1wt%, 1.5wt% and 2.0wt%) alloys were studied by OM, Pandat software, XRD, SEM, DSC and a standard universal testing machine. The experimental results indicate that adding Cu to TAZ811 alloy leads to the formation of the AlMgCu and Cu₃Sn phases. Tensile tests indicate that yield strength increases firstly and then decreases with increasing Cu content. The alloy with the addition of 1.5wt% Cu exhibits optimal mechanical properties among the studied alloys. The improved mechanical properties can be ascribed to the second phase strengthening and fine-grain strengthening mechanisms resulting from the more dispersed second phases and smaller grain size, respectively. The decrease in ultimate tensile strength and elongation of TAZ811-2.0wt% Cu alloy at room temperature is ascribed to the formation of continuous AlMgCu and coarse Mg₂Sn phases in the liquid state.