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.