Fabrication and characteristics of Al6061/SiC/Gr hybrid composites processed by in situ powder metallurgy method

A new method, namely in situ powder metallurgy, is applied for preparation of Al6061/SiC/Gr hybrid composites containing 20 vol.% of SiC particles with average sizes of 19, 93 and 146 µm, along with 0–13 vol.% uncoated graphite particles. For this purpose, SiC and graphite particles were added to molten aluminum alloy and the resultant slurries were stirred at 710°C for 8 min. During the stirring process, SiC and graphite particles disintegrated in the molten alloy, resulting in a mixture of SiC, graphite and aluminum alloy powder particles. After melt solidification, the powder mixtures were cold-pressed, sintered and heat-treated to obtain Al/SiC/Gr hybrid composites. Scanning electron microscope micrographs indicated a uniform distribution of SiC and graphite particles within the powder mixtures and hybrid composites. Moreover, smaller and more irregular-shaped aluminum particles were produced using finer SiC particles. The increased SiC particle size and graphite content resulted in improved compressibility of powder mixtures and decreased hardness of the hybrid composites. The improved wear resistance of these hybrid composites was obtained by using 5 vol.% graphite along with increased size of SiC particles.