Effect of Graphite Content on Characteristics Al/40SiC/Gr Hybrid Composites Processed by In situ Powder Metallurgy (IPM) Method

Aluminum matrix composites reinforced with SiC and Gr particulates are a unique class of advanced engineered materials that have been developed for use in tribological applications. Conventional liquid phase techniques and powder metallurgy (P/M) used for producing these composites have some drawbacks, such as poor wettability of the reinforcement particles with the matrix alloy, inhomogeneous distribution of particles, presence of Al4C3 compound and requiring a relatively long mixing time for obtaining a uniform distribution of reinforcing particles in the matrix. In the present study a relatively new method, namely in situ powder metallurgy (IPM) was applied for consolidating the Al/40SiC/Gr hybrid composites. In this method, stir casting and P/M synthesizing processes were combined into an integrated net shape forming process. In this work, the effect of graphite content (0-13 Vol.%) on characteristics of the resultant powder, green density of the Al/40SiC/graphite compacts as well as the microstructure and hardness of the consolidated hybrid composites was investigated. It was concluded that the increased graphite content was accompanied with finer aluminum particles and improved densification of the powder compacts. Hardness of all the composites were higher than the base alloy. However, hardness was decreased by enhancing graphite content of the composites.