Microstructure and mechanical properties of modified Mg-8Al-2Sn alloys using Zn addition combined with artificial aging treatment

The microstructures and mechanical properties of Mg-8Al-2Sn (AT82) base alloys with different Zn additions have been studied. The as-cast AT82 alloy consists of alpha-Mg, Mg17Al12 and Mg2Sn eutectic phases. Zn addition refines alpha-Mg dendrites and eutectic phases, and promotes the age-hardening response. When aged at 175 degrees C, the 13-Mg17Al12 precipitates are mainly formed in the studied alloys. The Zn addition reduces the discontinuous 13 precipitates near grain boundaries, meanwhile refines continuous 13 precipitates formed at the intragranular and increases the number density. Tensile tests indicate that the Zn addition and ageing treatment evidently improve the mechanical properties of AT82 base alloys at room temperature (RT) and 175 degrees C. The ATZ821 alloy with 1.0 wt% Zn addition exhibits an optimal combination of high strength and good ductility at both conditions. The ultimate tensile strength (UTS), yield strength (YS) and elongation to failure (Ef) of peak-aged state are 235 MPa, 147 MPa and 10.2% at RT, and 185 MPa, 122 MPa and 14.2% at 175 degrees C, respectively.