The effects of slurry preparation process and pouring temperature on the microstructure and mechanical properties of Al-Si-Cu-Si alloys were investigated.The results reveal that the Si phase in the alloy is passivated

however aggregation occurs after electromagnetic stirring.The size of primary Si is decreased after ultrasonic vibration treatment

of which the morphology is converted from dendrite to nearly sphericity.The count per unit area of Si phase particles reaches 0.46×10

3

/mm

2

with the roundness of 0.64

and the average grain size is 15.7μm.As the pouring temperature of slurry decreased from 620℃to 600℃

the microstructure is significantly refined

and the grain is coarsened as the decreasing in pouring temperature

with pore defects existing in the microstructure.When the slurry temperature is 600℃

the tensile strength of the alloy is 194 MPa

the elongation is 2.60%

and the hardness is 120.2 HB

which are improved by 10.23%

6.12% and 16.83%

respectively

compared with those of ones at 580℃.Meanwhile

the amount of fracture dimples is increased and the size of cleavage platform is decreased.