Effect of SiC content on the processing, compaction behavior, and properties of Al6061/SiC/Gr hybrid composites

Aluminum matrix composites reinforced with SiC and graphite (Gr) particles are a unique class of advanced engineered materials that have been developed to use in tribological applications. The conventional techniques for producing these composites have some drawbacks. In this study, a new method, namely In situ Powder Metallurgy (IPM), is applied for the preparation of Al6061/SiC/Gr hybrid composites. In this method, the stir casting and the powder metallurgy synthesizing processes are combined into an integrated net shape forming process. 0-40 vol.% of SiC particles with an average size of 19 mu m, along with 9 vol.% of uncoated Gr particles, were introduced to the molten 6061 aluminum alloy. Then, the slurries were stirred in a specified time-temperature regime resulting in mixtures of the SiC, Gr, and aluminum powder particles. The powder mixtures were cold pressed in six different pressures (between 250 and 750 MPa) and sintered. Finally, the produced composites were heat treated and their hardness and wear properties were investigated. Homogenous distribution of the SiC and Gr particles within the powder mixtures and the hybrid composites is clear from the SEM images. The results also show that the SiC particles decrease the compressibility of the hybrid powders and improve the hardness of composites. The best wear resistance is achieved in the hybrid composite containing 20 vol.% SiC particles.