The semisolid slurry of AM60 alloy was prepared by self-inoculation method

and the cold chamber die casting machine was employed to form the semisolid slurry under different injection speeds to investigate effect of injection speed on defects formation for rheo-diecastings.Insufficient filling was observed with the speed less than 0.5m/s

however

with increasing speed to less than 2m/s

the complete shape of castings was obtained along with the cold shut formation at the end surface of casting.In addition

with injection speed higher than 7m/s

serious flash defects were generated.Microstructural observation indicates that with increasing in injection speed

the amount and size of gas-pores in microstructure are increased

while liquid segregation is decreased

and the amount and size of inclusion is increased.With the injection speed less than 1m/s

the morphology of primary solid phase is deteriorated and the secondary dendrites in liquid are increased.Therefore

although a high injection speed can increase the microstructural uniformity of casting

the increased pore and inclusion defects also generated increasingly

which is not beneficial for the improvement of mechanical properties of semisolid castings.