An Investigation of the effect of silicon additions on the tribological properties of zinc-aluminium alloys

SUMMARY An Investigation of the Effect of Silicon Additions on the Tribological Properties of Monotectoid Zinc-Aluminium Alloys In this work, one binary zinc-aluminium and eight ternary zinc-aluminium-silicon alloys were produced by permanent mould casting. The friction and wear properties of the alloys were investigated in both as-cast and heat-treated conditions using a block-on-disc machine and related to their microstructure and mechanical properties. It was observed that the microstructure of the zinc-aluminium-silicon alloys alloy was consisted of aluminum-rich a, zinc-rich rj and silicon phases. The size and distribution of silicon phase in these alloys was found to be depend on their silicon content. The heat treatment removed the dendritic microstructure of the alloys and produced a fine-grained microstructure but had no considerable effect on the silicon particles. The hardness and the tensile strength of the alloys increased with increasing silicon content up to 2%Si, above which it decreased as the silicon content increased. It was also found that the coefficient of friction and the wear rate of the alloys decreased with increasing silicon content up to 2%Si, above which they increased as the silicon content increased. Among the experimental alloys, the best mechanical and wear behaviour was obtained with the Zn-40Al-2Si alloy. Silicon addition was found to be the very effective in improving mechanical and wear properties of zinc-based alloys. This work also showed that the wear behaviour of zinc based alloys is strongly depend on their hardness, tensile strength and coefficient of friction. Key Words: Zinc-Aluminium Alloys, Effect of Silicon, Friction and Wear