Microstructures and mechanical properties of extruded and heat treated Mg–6Zn–1Si–0.5Mn alloys

Abstract

Si-rich intermetallic particles stabilize the fine grained microstructure in extruded Mg–6Zn–1Si–0.5Mn alloy, resulting in a yield strength (YS) of ∼200MPa, ultimate tensile strength (UTS) of ∼310MPa with an elongation of ∼20%. Ca additions further refine the grain size leading to an increase in UTS by 30MPa with no decrease in YS and elongation. The extruded Mg–6Zn–1Si–0.5Mn alloy can be age-hardened with the precipitation of fine [0001]Mg rod-like β1′ (Mg4Zn7) particles and YS∼290MPa and UTS∼320MPa were achieved in the peak aged condition. The mechanical properties were further enhanced by pre-aging the alloy at 70°C due to the refinement of the precipitate microstructure with YS∼350MPa and UTS∼360MPa.