The effects of solution time on microstructures and mechanical properties of semi-solid forming hypereutectic Al-Si-Cu-Mg alloy were investigated.The results show that the solution treatment can improve the microstructures and mechanical properties of the alloy.With the increase of solid solution time

the eutectic Si phase is necked

melted and granulated

and the primary Si phase is passivated

meanwhile the Al

2

Cu equivalent strengthening phases are decreased

which are responsible for the improvement of mechanical properties of the semi-solid alloy.The tensile strength

yield strength and hardness of the alloy reach 311 MPa

291 MPa and 132.0 HB

respectively

after solution treatment for 10 h.With the solid solution time further increase

the eutectic Si is grown

So the mechanical properties of the semi-solid alloy are decreased.