Effect of Particulate Size on the Microstructural Evolution, Aging Behavior and Mechanical Properties of Al-4.5 Cu/SiC Composites

Abstract

In the present study, an aluminum based metallic matrix (Al-4.5wt.% Cu) was successfully reinforced with SiC particulates of two different sizes using an innovative disintegrated melt deposition technique. The results of microstructural characterization studies revealed that smaller SiC particulates (8 μm) lead to a more equiaxed matrix grain morphology when compared to the larger SiC particulates (34.4 μm). The matrix grain morphology results were rationalized in terms of particulate-size influenced movement and destabilization of the solid-liquid interface. The results of the aging studies revealed an accelerated aging kinetics in the case of composite samples containing 8 μm SiC particulates when compared to the composite samples with 34.4 μm SiC particulates and unreinforced samples. The accelerated aging kinetics which is unusual in case of aluminum matrices containing copper in excess of 4 weight percent was rationalized in terms of particulate size associated variation in microstructural features. Results of ambient temperature mechanical tests revealed an increase in 0.2% yield strength and decrease in ultimate tensile strength and ductility in the case of composite samples when compared to the unreinforced samples in the as-processed condition. The mechanical properties characterization results were found to reveal direct correlation with the variation in microstructural features of the metallic matrix such as grain size and dislocation density originating due to the presence and different sizes of SiC particulates.