In this study, A357 (Al-7%Si-0.5%Mg) alloy/Al2O3 composites with various volume fractions (4%, 8%, 10%) were prepared by using permanent mould casting. In addition, A357 alloys were cast for comparison purposes. The alloys and composites were given a T6 heat treatment process (solution treatment and artificial ageing), Also microstructure, hardness and tensile properties of these composites were evaluated and compared. In addition, tribological properties of these composites were evaluated using a Pin-on-Disc apparatus at a constant sliding velocity of 1m/s and pressure of 0.35 MPa. The microstructure of the composites shows homogenous distribution of Al2O3 plate-like particles in the Al matrix except in the A357/10%Al2O3 composite. The wear and mechanical properties of composites improve with increasing the volume fraction of Al2O3 upto 8% and then decreases. Particularly, mechanical properties of the A357/10%Al2O3 composite are lower than the alloy indicating that the critical volume fraction of Al2O3 reinforcement in the A357 alloy is 8%. Wear morphology studies show that abrasive and delamination wear are extensive in the alloy whereas the slight delamination wear with some abrasive grooves are found in the composites.
