Influence of Sn addition on the microstructure and mechanical properties of extruded Mg-8Al-2Zn alloy

The effect of adding Sn to an extruded Mg-8Al-2Zn (AZ82 alloy) was investigated by analyzing its microstructural characteristics before and after extrusion, and by conducting tensile and compressive tests with 2, 4, and 6wt% Sn addition. This revealed that although second phases formed during solidification are nearly fully dissolved by homogenization treatment in AZ82 alloy with 2wt% Sn, numerous Mg₂Sn particles remain in AZ82 alloys with 4 and 6wt% Sn due to this concentration being over the solubility limit. All of the extruded alloys were found to have a fully recrystallized structure, yet the addition of 6wt% Sn created a considerable quantity of large, banded Mg₂Sn particles oriented along the extrusion direction. The tensile and compressive yield strength gradually increased with Sn content mainly due to a decrease in the size of recrystallized grains and an increased amount of fine Mg₂Sn precipitates, though this came at the expense of a decrease in elongation. It was also found that the ultimate tensile strength improves with Sn addition of up to 4wt%, but deteriorates beyond that point due to premature fracture caused by crack initiation at large particles.