Relationship between microstructure and mechanical properties of as-extruded and peak-aged Mg-6Al-3Sn-2Zn alloys

The microstructure and mechanical properties of as-extruded and as-aged Mg-6Al-3Sn-2Zn (ATZ632) alloys were investigated. The as-extruded alloy shows excellent mechanical properties, achieving the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of 216.4 MPa, 344.3 MPa, and 18.4%, respectively. After aging treatment, the volume fraction of the precipitated Mg17Al12 phase increases and the Mg4Zn7 phase appears. The YS and UTS of the as-aged ATZ632 alloy increased to 252.5 and 416.2 MPa, respectively; however, the EL decreased to 10.1%. The high strength of the as-aged alloys is attributed to the precipitated Mg4Zn7 phase with an orientation perpendicular to the (0001) plane of alpha-Mg and the Mg17Al12 phase with an orientation parallel to the basal plane. Furthermore, the precipitation after aging decreases the EL. Static recrystallization grains appear during low-temperature aging at 150 degrees C, and their orientation shows a high degree of consistency with the c-axis perpendicular to the extrusion direction.