Wear behavior of secondary processed spray formed Al-28Si-5Cu-4Mg alloy

Abstract

In the present study Al-28Si-5Cu-4Mg alloy has been spray formed and hot pressed for densification. Hot pressing refined the microstructure and reduced the porosity in the spray formed alloy from 10 to 1%. The microstructure of spray formed and hot pressed alloy exhibited equiaxed grain morphology with fine and uniform distribution of both primary and eutectic Si with fine needles of Q-Al 12 Si 7 Mg 4 Fe intermetallics and Chinese script like θ- Al 2 Cu precipitates in α-Al matrix. The size of Si particles ranged from 3–10 µm. In contrast the microstructure of as-cast alloy consisted of coarse primary and eutectic Si, long needles of Q-Al-Si-Mg-Cu-Fe phase and bright grey θ-Al 2 Cu phase in the α-Al matrix. The size of primary Si varied from 30–250 µm. The spray formed and hot pressed alloy exhibited a higher hardness compared to the as-cast alloy. The wear behavior of both the alloys, under dry sliding conditions, showed an increase in the wear rate with an increase in the load. However, the spray formed and hot pressed alloy exhibited maximum wear resistance and minimum coefficient of friction, while as-cast alloy exhibited minimum wear resistance and maximum coefficient of friction over the entire range of applied load. The high wear resistance and high hardness of spray formed and hot pressed alloy are explained in the light of its microstructural modifications induced during spray forming and subsequent hot pressing and also the topographical features of worn surfaces and morphology of debris particles.