The microstructures and properties of squeeze casting hypereutectic Al-17.5Si alloy after hot extrusion were analyzed.The results show that there are some effects of squeeze casting parameters on the microstructure of hypereutectic Al-17.5Si alloy

and the eutectic structure is refined significantly

and coralline eutectic Si phase is transformed into small needle-like ones.With the squeeze casting pressure increase

the coarse primary Si phases are reduced significantly and theα-Al dendrites are generated with more developed shape.After hot extrusion

microstructures of the squeeze casting hypereutectic Al-17.5Si alloy is changed greatly

and the absence of developedα-Al dendrite can be observed

and the small needle-like eutectic Si phases are broken into particles

and then are dispersed uniformly in the matrix of alloy after severe deformation.After hot extrusion forming

the properties of the squeeze casting hypereutectic Al-17.5Si alloy are improved greatly

especially the plasticity.After the hot extrusion forming of the squeeze casting billets at 320 MPa

tensile strength and elongation of the alloy reach158.82 MPa and 11.65%

respectively

which are increased by 84.13% and 441.86%

compared with those of the casting alloy.