Microstructure, mechanical and corrosion properties of Mg-4Al-2Sn-xY-0.4Mn alloys

The effects of Y addition (0, 0.5 and 1.0 wt. %) on the microstructure, mechanical properties and corrosion behavior of Mg-4Al-2Sn-0.4Mn alloy have been investigated. The results indicate that the addition of Y leads to the formation of irregular polygonous massive Al2Y phase and the average size of Al2Y increases with increased Y content. The reticular β-Mg17Al12 phase is refined and its amount reduced due to the newly formed Al2Y phase distributing along grain boundaries. Meanwhile, the yield and tensile strengths are improved by the Y addition, which are mainly attributed to the promotion of dynamic recrystallization (DRX) by particle-stimulated nucleation (PSN) around relative small Al2Y particles and the weakness of basal textures. Optimal comprehensive mechanical properties are obtained for the cast-extruded alloy with 1.0 wt.% Y, which has YS and UTS of 242 MPa, 318 MPa with an elongation of 13.3%. The corrosion resistance of the cast-extruded alloys is also discussed, and Mg-4Al-2Sn-0.5Y-0.4Mn alloy exhibits best corrosion resistance.