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

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.