A new high-strength extruded Mg-8Al-4Sn-2Zn alloy

The microstructure and mechanical properties of a newly developed high-strength Mg-8Al-4Sn-2Zn alloy (ATZ842) were investigated and compared with those of a commercial high-strength Mg-8Al-0.5Zn alloy (AZ80). The presence of undissolved second phases and the small grain size of homogenized ATZ842 were found to promote dynamic recrystallization (DRX) during extrusion through particle-stimulated nucleation (PSN) and an increase in nucleation sites for DRX, respectively. The extruded ATZ842 was subsequently found to exhibit greatly superior mechanical properties to AZ80 extruded under the same conditions, with a tensile yield strength of 371MPa, an ultimate tensile strength of 415MPa, an elongation of 9.1%, and a low tension-compression yield asymmetry of 1.02 all being recorded. These excellent mechanical properties are attributed to the combined effects of grain refinement, an increase in the recrystallized fraction, enhanced dispersion and precipitate strengthening, and improved solid-solution strengthening.