Effects of silicon carbide reinforcement on microstructure and properties of cast Al-Si-Fe/SiC particulate composites

The effects of silicon carbide (SiC) particles on the as-cast microstructure and properties of Al-Si-Fe alloy composites produced by double stir-casting method have been studied. A total of 5-25 wt% silicon carbide particles were added. The microstructure of the alloy particulate composites produced was examined, the physical and mechanical properties measured include: densities, porosity, ultimate tensile strength, yield strength, hardness values and impact energy. The results revealed that, addition of silicon carbide reinforcement, increased the hardness values and apparent porosity by 75 and 39%, respectively, and decreased the density and impact energy by 1.08 and 15%, respectively, as the weight percent of silicon carbide increases in the alloy. The yield strength and ultimate tensile strength increased by 26.25 and 25% up to a maximum of 20% silicon carbide addition, respectively. These increases in strength and hardness values are attributed to the distribution of hard and brittle ceramic phases in the ductile metal matrix. The microstructure obtained reveals a dark ceramic and white metal phases, which resulted into increase in the dislocation density at the particles-matrix interfaces. These results show that better properties is achievable by addition of silicon carbide to Al-Si-Fe alloy.