A new type high strength and heat resistant Mg-10Gd-Y-Zr（GW103K）magnesium alloy semi-solid slurry was prepared by the near liquidus casting method

and its microstructure was compared with that prepared by over-liquidus casting method.And the effects of holding time and cooling rate of the mould on the as-cast microstructure of the alloy were investigated in near-liquidus casting method.The results reveal that compared with that prepared by over-liquidus casting

microstructure of the GW103K semi-solid slurry prepared by near-liquidus casting is obviously changed.Near-liquidus casting is beneficial to the spheroidization of grain size in the GW103K containing Zr with obviously increasing in roundness

However

grain size becomes coarse as a result of fusion mechanism.With increasing in holding time

grain size is increased with the great decrease of roundness

while grain boundary is refined due to the reduction of intermetallics distributed along the boundary.With increasing in cooling rate

the grain size in the alloy is refined with the increase of shperoidization.The new type high strength and heat resistant magnesium alloy GW103K slurry with more perfect spheroidized structure can be prepared by near-liquidus casting method by the molten alloy immediately pouring into a high cooling capacity mould at near-liquidus temperature.