Abstract:To improve the wear resistance of cast Al-17Si-5Cu alloy (AR alloy), isothermal heat treatment is employed to modify the morphology of Si particles (particularly eutectic Si particles). Furthermore, wear behaviour of heat-treated alloy (HT alloy) along with AR alloy is studied using a pin-on-disc tribometer. Worn surfaces are then characterised using scanning electron microscope. The result reveals considerable microstructural modifications after the heat treatment. Accordingly, higher hardness value in HT alloy is obtained compared with AR alloy. The overall wear rate for HT alloy is found to be significantly lower compared with AR alloy at all the applied loads, indicating remarkable improvement in wear resistance. Eutectic Si particles become from acicular/rod-like to spherical/equiaxed morphology (aspect ratio close to 1) on heat treatment, resulting in good bonding with the matrix. Thus, they remain intact during wear and being harder, providing resistance to wear. Moreover, the increased hardness on heat treatment causes further resistance to wear. Therefore, the combined effect of intact harder Si particles on the wearing surface and higher hardness results in superior wear behavior in HT alloy at all loads compared with AR alloy.

Key words: heat treatment; abrasive wear; hypereutectic Al-Si alloys