Effect of Sn content on microstructure and tensile properties of as-cast and as-extruded Mg?8Li?3Al?(1,2,3)Sn alloys

The effects of Sn content on microstructure and tensile properties of as-cast and as-extruded Mg?8Li?3Al? (1,2,3)Sn (wt.%) alloys were investigated by X-ray diffractometry (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and tensile test. It is found that, as-cast Mg?8Li?3Al?(1,2,3)Sn alloys consist of α-Mg+β-Li duplex matrix, MgLiAl₂ and Li₂MgSn phases. Increasing Sn content leads to grain refinement of α-Mg dendrites and increase in content of Li₂MgSn phase. During hot extrusion, complete dynamic recrystallization (DRX) takes place in β-Li phase while incomplete DRX takes place in α-Mg phase. As Sn content is increased, the volume fraction of DRXed α-Mg grains is increased and the average grain size of DRXed α-Mg grains is decreased. Increasing Sn content is beneficial to strength but harmful to ductility for as-cast Mg?8Li?3Al?(1,2,3)Sn alloys. Tensile properties of Mg?8Li?3Al? (1,2,3)Sn alloys are improved significantly via hot extrusion and Mg?8Li?3Al?2Sn alloy exhibits the best tensile properties.