The effect of processing on the mechanical properties and interfacial strength of aluminium/TiC MMCs

The microstructure and mechanical properties of aluminium/TiC MMCs made by powder processing (PM), by a flux-casting process, and by melting PM materi al, have been compared. Particle clustering is more prevalent in cast than in PM composites, but the grain-refining nature of TiC particles significan tly reduces the degree of clustering commonly observed in cast MMCs. Meltin g PM material enables oxide films to 'trawl' the particles into large clust ers. The stiffness and ductility are similar for cast and the PM composites but melting the PM material results in significant reductions in strength and ductility. In all cases, composite ductility is enhanced by extrusion t hrough the removal of porosity and the break-up of particle clusters. Modul us measurements as a function of plastic strain indicate that rates of dama ge accumulation are lowest, and hence interfacial bonding is strongest, in cast composites as a result of the attainment of intimate contact and stron g chemical bonding between the two phases. (C) 2000 Elsevier Science Ltd. A ll rights reserved.