Effect of Heat Treatment on Mechanical Properties, Microstructures and Wear Resistance of Al-Si-Cu Alloy

Mechanical properties, microstructure and wear performance of Al-Si-Cu alloy after heat treatment were investigated. The results show that T6 heat treatment rendered the alloy finer microstructure (matrix and uniformly distributed second phases, i.e. Si phase, Al₂Cu phase and AlFeMnSi phase) in comparison with the as-cast alloy. The mechanical properties and wear performance of T6 state alloy are better than that of the as-cast alloy. At load lower than 500 N, T6 state alloy and cast-quenching state alloy had comparable wear performance with dominant wear mechanism of abrasive wear. At load between 500 N and 1 000 N, horizontal plastic flow stress gave birth to uniformly distributed Si phase on the worn surface, which improved the tribological performance. In addition, transition of abrasive wear to abrasive wear and adhesive wear occurred. At load higher than 1 000 N, micro cracks and severe tearing plastic deformation around the Si phase and Al₂Cu phase were observed and this increased the friction coefficient. The wear mechanism transformed to delamination wear and the wear performance of the alloy became worse.