The present work reveals the A356 aluminium alloy reinforced with a mix of silicon carbide (SiC) and multi-walled carbon nanotubes (MWCNTs), using a combined stir cum squeeze casting route. The hybrid reinforcements were introduced at 5, 10, 15 and 20 wt.% while keeping a 2:1 SiC-to-MWCNT ratio. Applying 100 MPa pressure during solidification reduced porosity and helped the particles settle into a much more uniform microstructure. As the reinforcement level increased, the composites showed steady improvements in hardness, yield strength and ultimate tensile strength. These gains appear to branch from the rise in thermally induced dislocation density caused by the mismatch in thermal expansion between the reinforcements and the aluminium matrix. The machinability results were a quite complicated. Higher cutting speeds generally lowered cutting forces, and the hybrid reinforcements helped minimise built-up edge formation, which in turn improved surface quality. At similar machining conditions, the cutting forces of the hybrid composites were consistently lower than typical values reported for composites reinforced with SiC alone. At the end, the study shows that stir cum squeeze casting is a reliable way to produce dense, mechanically strong A356 hybrid composites with encouraging machinability characteristics. These findings position the material as a promising option for lightweight components, especially where both strength and workability matter.
Pathinettampadian et al. (Sat,) studied this question.