Effects of Mn addition on the microstructure and mechanical properties of cast Mg–9Al–2Sn (wt.%) alloy

Abstract

Abstract The microstructure and mechanical properties of cast Mg–9Al–2Sn–xMn (x = 0, 0.1, 0.3 wt.%) alloys in as-cast, solution treated and aged conditions are investigated. The results reveal that Mn addition into Mg–9Al–2Sn alloy leads to the formation of Al8(Mn,Fe)5 phases, the grain refinement and the increase of discontinuous Mg17Al12 precipitates along the grain boundaries. 0.1 wt.% Mn addition has an obvious effect on accelerating the aging behavior of Mg–9Al–2Sn alloy at the early aging period up to 8 h, while 0.3 wt.% Mn addition alloy has an comparable aging behavior with the Mn-free alloy. Mn addition has less influence on the fracture behavior of Mg–9Al–2Sn alloy, while the fracture pattern is mainly determined by the thermal conditions. Mg–9Al–2Sn–0.1Mn alloy has the best combination of strength and elongation when aged at 200 °C for 8 h and the yield strength, ultimate tensile strength and elongation are 154 MPa, 292MPa and 5%, respectively.