Effect of reinforcement volume fraction on the evolution of reinforcement size during the extrusion of Al-SiC composites

The effect of reinforcement volume fraction on the evolution of the reinforcement particle size during extrusion was investigated for the Al-SiC model composite system. Composites with 6.4, 10.0, and 16.8 volume percent of SiC particles were extruded at a temperature of 350 °C using an extrusion ratio of 12:1. Image analysis showed that the SiC particles were refined by the extrusion process and that the extent of the refinement increased with an increase in reinforcement volume fraction. A mechanistic rationale for the experimentally observed trends is formulated with reference to the corresponding change in the stress fields in the composite microstructure with the change in the reinforcement volume fraction. Possible implications of extrusion-induced particle fracture for the processing of fine particle-reinforced metal matrix composites are also explored in this paper.