Evolution of microstructure and its effect on wear and mechanical properties of spray cast Al–12Si alloy

In the present study, the microstructural features, mechanical properties and wear characteristics of spray cast Al–12Si alloy have been investigated and compared with that of the chill cast alloy. The spray cast alloy was subjected to hot isostatic pressing for reducing the porosity of the deposit from 26% to 6%. The microstructure of the spray cast and hot isostatically pressed alloy consisted of finely divided globular shaped eutectic Si uniformly distributed in the Al matrix. The fine particles of Si were invariably observed in the bottom and top regions of the spray-deposit in contrast to relatively large size Si particles in the central region. The microstructure of the chill cast alloy was coarse and consisted of an eutectic mixture of α-Al and Si needles. The room temperature tensile tests and hardness measurements showed improved mechanical properties of spray cast alloy over that of the chill cast alloy. In addition, the dry sliding wear test indicated a superior wear resistance of the spray cast alloy over a wide range of sliding velocity. This behavior of the spray cast alloy is discussed in the light of its microstructural modification induced by spray casting.