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

摘要

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 30 MPa 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 β_1 (Mg_4Zn_7) particles and YS ～ 290 MPa and UTS ～ 320 MPa were achieved in the peak aged condition. The mechanical properties were further enhanced by pre-aging the alloy at 70 ℃ due to the refinement of the precipitate microstructure with YS ～ 350 Mpa and UTS～360 Mpa.