Damage evaluation in discontinuously reinforced aluminum matrix composites subjected to thermal cycling

A comparative study of the damage in the powder metallurgy processed Al–Cu–Mg alloy–SiC (as-extruded and solution-treated) and Al–SiC (hot rolled), and in situ cast Al–TiC (as-extruded) composites, each with 15 vol.% particulate reinforcements, has been carried out. Repeated thermal cycling of the composites between 500 and 0 °C was followed by evaluation of damage by examination of microstructure using scanning electron microscopy, determination of changes in dynamic Youngʹs modulus, and measurement of microhardness near the reinforcement–matrix interfaces. The thermally cycled Al alloy–SiC composites have exhibited reduction in Youngʹs modulus and microhardness adjacent to reinforcement–matrix interfaces, due to decohesion caused by thermal mismatch strains. In contrast, the SiC or TiC reinforced Al composites subjected to thermal cycling, have shown only a marginal reduction in the Youngʹs modulus, and cracks in the Al matrix rather than at interfaces, near which microhardness increment by strain-hardening through dislocation generation has been noticed.