Enhancement of mechanical and tribological properties of SiC- and CB-reinforced aluminium 7075 hybrid composites through friction stir processing

Aluminium alloy has wide application in both aircraft and automobile industry due to its high strength and light weight benefits. In this research work, stir casting process was used for fabricating aluminium alloy 7075 reinforced by silicon carbide (SiC) and carbon black (CB) particulates. X-ray diffraction analysis, energy dispersive X-Rays analysis and field emission scanning electron microscopy (FE-SEM) confirmed the presence of SiC and CB particles and there uniform distribution in aluminium matrix. Further, as-cast composites have been processed by friction stir processing (FSP) technique with the appropriate processing parameter: tool speed, feed rate and tool tilt angle. Mechanical and microstructural properties of the composites before and after FSP were investigated through universal testing machine and optical microscopy. The novel feature of as-cast AA7075/SiC/CB is that it demonstrates a 2.5 times increment in the ultimate tensile strength and at the same time, significant amount of increased ductility. Ductile failure may be possible fracture mechanism as shown in FE-SEM analysis. Further, the tribological behaviour of the synthesized composites studied under dry sliding conditions before and after FSP and the results indicates significant improvement in wearing capacity of the composites. Also, weight loss of the various composites by varying three input variable process parameters were investigated followed by analysis of variance and regression analysis. The presence of 5 wt.% SiC and 5 wt.% CB in the composites can exhibit superior mechanical as well as wear property as compared to base alloy.