Effects of Sn addition on microstructure and mechanical properties of Mg-Zn-Al alloys

The effects of Sn addition (0, 0.5, 1.0, 2.0 and 3 wt%) on microstructure of Mg-4Zn-1.5Al alloy in cast and extruded states were investigated, and the mechanical properties of as-extruded Mg-4Zn-1.5Al-xSn studied. The experimental results showed that the as-cast Mg-4Zn-1.5Al alloy was composed of two phases alpha-Mg and Mg-32 (Al, Zn) 49, while Sn-containing alloys consisted of a-Mg, Mg-32 (Al, Zn) 49 and Mg2Sn phases, and Mg-32 (Al, Zn) 49 was not detected after extruding due to that the most of them dissolved into the matrix during the homogenized treatment. The addition of Sn refined the grains of as-cast and as-extruded Mg-Zn-Al alloys obviously. It was noted that the basal texture intensity reduced with increasing Sn content significantly in as-extruded Mg-Zn-Al alloys. The tensile tests results indicated that Sn addition improve the tensile strength of the extruded alloys, while it had a harmful effect on the ductility. When the addition of Sn was 2 wt%, the ultimate tensile strength (UTS), yield strength (YS) and elongation (epsilon(f)) of the alloy were 280 MPa, 147 MPa and 17.4%, respectively.