Effect of Zn addition on the microstructure and mechanical properties of cast, rolled and extruded Mg-6Sn-xZn alloys

Tin and zinc have great potential as alloying elements in magnesium alloys in which they have a wide range of solid solubility. In the present study, the microstructure and mechanical properties of Mg-6Sn-xZn (x=0, 2, and 4 wt%) were investigated and compared in cast/heat treated, rolled at 350 °C from 10 mm to 2 mm and extruded at 350 °C with a ratio 40:1. The alloy composition and the applied process affected the mechanical properties. The Young's modulus increased with increasing Zinc content up to 2% and reached a maximum value of 40 GPa for the Mg-6Sn-2Zn alloy. In the case of the cast/heat treated condition, the ultimate tensile strength (UTS) and elongation to rupture increased with the Zn content, reaching maximum values of 189.7 MPa and 7.15%, respectively, for the Mg-6Sn-4Zn alloy. The maximum strength of the alloys in the rolled conditions was achieved for Mg-6Sn-4Zn alloy with a value of 253 MPa with 12.32% elongation while in the extruded conditions the Mg-6Sn-4%Zn alloy exhibited a maximum combination of strength and elongation of 276.33 MPa and 23.1%, respectively. The results are discussed with respect to the microstructure evolution, grain size and precipitates in the alloys.