Effect of Matrix Constitution on Microstructure and Mechanical Properties of Rheocast Metal Matrix Composites

In this study, aluminum-based metallic matrices with varying amounts of copper (I wt.% Cu, 3 wt.% Cu and 4.5 wt.% Cu) were reinforced with SiC particulates using a partial liquid phase casting technique. Microstructural characterization studies conducted on the composite samples revealed an increase in uniformity of distribution of SiC particulates and SiC/Al interfacial integrity and a decrease: in porosity in the metallic matrix with decreasing weight percent of copper. The results of the ageing studies revealed an accelerated ageing kinetics for the Al-1% Cu/SiC composite when compared to Al-3% Cu/SiC and Al-4.5% Cu/SiC samples. Results of ambient temperature mechanical tests demonstrate an increase in 0.2% yield strength and ultimate tensile strength of the composites and a decrease in ductility and strain hardening rate with an increasing weight percent of copper in the metallic matrix. Fracture studies revealed the presence of interfacial debonding, particulate breakage and cracks in the matrix of tensile specimens. The results of microstructural characterization, mechanical testing and fractography were finally rationalized in terms of the effect of variation in weight percent of copper in the metallic matrix.