Particle size effect on the interfacial properties of SiC particle-reinforced Al-Cu-Mg composites

In particle-reinforced metal matrix composites, geometrically necessary dislocations (GNDs) form on the matrix side close to the particle/matrix interface. The mechanical behavior of the bulk composite is affected by the nature of the region populated with GNDs. In this study, the hardness evolution across the reinforcement/matrix interface in 15 vol% SiC particle (SiCp)-reinforced 2009 Al composites with varying particle sizes were studied by nanoindentation with high spatial resolution. The hardness data were then correlated with the microstructures of the composites as well as their bulk tensile properties. It was found that decrease in particle size was associated with a reduction in the punched zone width and an enhancement in the strength of the bulk composite. These findings were interpreted by the effect of GNDs on the ageing kinetics of the matrix, and the improved load-transfer capability through the reinforcement/matrix interface in composites reinforced by smaller particles.