Effect of processing techniques on the mechanical and wear properties of Al-20Si alloy

In the present investigation, the mechanical and wear properties of Al-20Si alloy processed by spray casting and vertical centrifugal casting processes have been evaluated and compared. In spray casting process the melt was gas atomized and the spray-deposited over a copper substrate. The spray-deposit exhibited considerable porosity and subjected to hot isostatic pressing to reduce the porosity from 19 to 2%. The centrifugal casting process provided cylindrical shaped preform with characteristically low porosity. The microstructure of spray cast alloy showed ultra fine and uniformly distributed primary and eutectic Si particles in the Al matrix. In contrast, a coarse polyhedral shaped morphology of the primary Si phase was observed in the microstructure of the centrifugal cast alloy. The wear rate of spray cast alloy was invariably lower than that of centrifugal cast alloy. The room temperature tensile and hardness tests of spray cast alloy showed considerable improvement in its strength, ductility and hardness over that of centrifugal cast alloy. The improvement in wear properties of spray cast alloy is discussed in the light of its microstructural modification induced by spray casting and nature of debris particles generated during wear testing.