Development of particulate treatments and coatings to reduce SiC degradation by liquid aluminum

Abstract

SiC-particulate-reinforced aluminum alloys are potentially attractive materials for structural applications. Among the fabrication possibilities, the molten metal mixing technique is one of the most promising in terms of cost and production capacity. Degradation of SiC by chemical reaction with molten aluminum is a problem that could be, at least partially, overcome by treatments or coatings of the reinforcements. This article describes the various techniques that have been used to coat particles and presents results ob-tained during remelting of composites. Prior oxidation of particles, oxide coating by sol-gel, or dry mixing techniques are thus presented. Oxidation of particles and TiO2 coatings slow the degradation of SiC. Analytical electron microscopy was used to characterize the interfacial reactions that occurred during fabrication and remelting of composites. Possible mechanisms of protection are then presented and discussed.