Effect of Cu and Mg on the wear properties of spray formed Al -22Si alloy

Abstract

In the present study, the effect of Cu and Mg on the wear behavior of spray formed Al-22Si alloy has been investigated and the same has been compared with that of its counterpart as-cast alloy. Al-22Si and Al–22Si–4Cu–1.7Mg alloys prepared by spray deposition process were hot pressed to reduce the porosity. The microstructures were examined by optical and scanning electron microscopes. The microstructure of spray formed Al-22Si alloy is fine and homogeneous and primary silicon phase distributed in the aluminum matrix evenly are fine and faceted having a mean size of 12 µm. The microstructure of spray formed Al–22Si–4Cu–1.7Mg alloy exhibited equiaxed grain morphology with fine and uniform distribution of both primary and eutectic Si with fine Q-Al-Si-Mg-Cu phase and θ-Al 2 Cu precipitates dispersed evenly in α- Al matrix. In contrast the microstructure of as-cast Al–22Si alloy consisted of coarse plates of primary Si of size 350 µm and eutectic Si needles. The as-cast Al–22Si–4Cu–1.7Mg alloy consisted of coarse primary Si with Chinese script like θ-Al 2 Cu precipitates and needles of Q-Al- Si-Mg-Cu phase in α-Al matrix. The wear study of both as-cast and spray formed and hot pressed alloys under an applied load of 10 to 50 N and sliding velocity of 0.4 to1.5 ms -1 indicated two distinct regimes of mild and severe wear. In both the regimes, the spray-formed and hot pressed alloys consistently indicated a low wear rate compared to that of as-cast alloys. The high wear resistance of spray formed and hot pressed Al–22Si and Al–22Si–4Cu–1.7Mg alloys were explained in the light of their microstructural modifications induced during spray forming and subsequent hot pressing.