Heat resistant Mg-RE （Mg-11Y-5Gd-2Zn-0.5Zr） alloy engine piston was produced by gravity casting

and the processing parameters

such as pouring temperature

preheating temperature of the mould and heat treatment conditions

were optimized.Meanwhile

the microstructure of alloy piston was observed by optical microscope

SEM （scanning electron microscope）.The results reveal that there exist amounts of secondary phases distributed along grain boundary in as-cast microstructure

while amounts of lamellar phases are precipitated from grain boundary after solid solution and ageing treatment.The Vickers-hardness of aged alloy piston shirt reaches 131.4

and high temperature tensile strength of piston top exhibits excellent with 161.9MPa at 350℃.In addition

creep strain of piston top is only 0.428% at 250℃/80MPa for 100 hours.The density

specific heat capacity at 100℃

thermal conductivity at room temperature and linear expansion coefficient at 20～100℃ reach 1.995g/cm3

850J/（kg·K）

23W/（m·K） and 25.6×10-6/K

respectively.