Influence of Initial Microstructure on the Strengthening Effect of Extruded Mg-8Sn-4Zn-2Al Alloys

The Mg-8Sn-4Zn-2Al (TZA842, in wt%) alloys with different initial microstructure (as-cast-AC and homogenization treatment-HT) subjected to hot extrusion. Also, the strengthening responses to AC and HT for the extruded TZA842 alloys were reported. The results revealed that the alloy subjected to HT shows finer grain size, more homogenous microstructure and weaker basal texture than those of counterpart subjected to AC. In addition, compared with TZA842-AC alloy, precipitates were finer and uniformly dispersed in TZA842-HT owing to the utilization of HT. Moreover, the TZA842-HT alloy showed higher yield strength of 200 MPa, ultimate tensile strength of 290 MPa and elongation (EL) of 17.9% than those of TZA842-AC, which was mainly attributed to the combined effects of grain boundary strengthening, precipitation strengthening, solid solution strengthening and weak texture. Strengthening mechanism for both alloys was discussed in detail.