The Mg-9Gd-1Y-0.5Zr(GW91) alloy piston was produced by squeezing casting.The mechanical properties of the samples cut from piston top and skirt at the peak-aged condition(T6) and its creep resistance at 200~300 ℃ were investigated.The results reveal that precipitates in grain is uniformly distributed in the T6 treated piston

and the grain size in piston top and skirt treated by T6 reaches 140 μm and 80μm

respectively.Meanwhile

the tensile strength of piston is decreased with increasing in temperature

and the ultimate tensile strength(UTS) of piston top and skirt are 210 MPa and 223 MPa

respectively

at 300 ℃.The steady-stage creep rate of piston is increased with increasing in temperature and applied stress.The steady-stage creep rate of piston top and skirt are 7.81×10-8 s-1 and 1.45×10-7 s-1

and total creep strain after 100 h are 2.8% and 3.0%

respectively

at 300 ℃ and 50 MPa

evidently superior to those of commercial Al-Si alloy.