Processing and mechanical properties of SiC particulate reinforced AZ91 composites fabricated by stir casting

The influence of stirring parameters (stirring temperature, stirring speed and stirring time) on the particle distribution of 10%(volume fraction) SiC particulate reinforced AZ91 composites (SiCp/AZ91) was studied. It is found that it is necessary for 10μm SiC particulate reinforced AZ91 composites to stir the molten composites in semi-solid condition with vortex formation, or else the cluster of the reinforcements would not be eliminated. Compared with the monolithic alloy, the SiCp/AZ91 composite has higher strength, especially for yield strength, but the elongation is reduced. For the as-cast composite, the particles often segregate within the grain boundary regions. Extrusion can effectively reduce the segregation of SiC particles and improve the mechanical properties of the composite. The extrusion-induced reduction in particle size varies with extrusion temperatures and extrusion ratios. The effect of extrusion-induced reduction in particle size on the mechanical properties of the composites is not always beneficial.