Microstructure and mechanical properties of solution heat-treated Al-5.5%Si-4%Cu alloy with different applied solidification pressures have been investigated. With the pressures applied during solidification

the microstructure of the alloy has shown significant change

and both tensile strength and elongation of the alloy were improved remarkably. As the squeeze pressure increase in the range from 0.1 MPa to 50 MP

size of primary α-Al was decreased evidently and morphology of eutectic Si particles was changed from long acicular to small granular

and the dendrite arm spacing

content of Al2Cu phase and porosities between dendrites were decreased while the mechanical properties increase. When the applied pressures changed from 50 MPa to 100 MPa

the microstructure and mechanical properties of the investigated alloy have been shown little variation. It is indicated that 50 MPa is a proper squeeze pressure of the investigated alloy whose tensile strength and elongation reached up to 323.6 MPa and 8.51%

respectively

at the applied pressure after solution heat treatment.