Development of aluminium-based composites reinforced with steel and graphite particles: structural, mechanical and wear characterization

Apparent limitations in toughness and ductility of ceramic reinforced aluminium matrix composites have prompted considerations of metallic reinforcements. In the present study, the structural characteristics, mechanical and wear behaviour of stir cast Al-Mg-Si alloy-based composites reinforced with different weight percent of steel-, steel-graphite hybrid mix-, and SiC-particles were investigated. The results show that the hardness of the composites increased approximately by 11% with increase in steel particles from 4 to 8 wt.%. For the same range of steel concentration, the ultimate tensile strength also increased with increase in steel wt.%. These strength values were all higher than that of 8 wt.% reinforced SiC by a margin of 3.2–24%. The specific strength and fracture toughness equally followed the same trend with respect to steel concentration with strain to fracture, the exception where slight decrease (less than 4%) is observed. For these properties, the values were superior to the SiC reinforced composite and ascribed to improved grain refinement and interface bonding, and the inherent ductility of the steel particles. For the 8 wt.% hybrid reinforced composite compositions containing steel and graphite, all the mechanical properties decreased slightly with increase in graphite content and trailed the composite reinforced with 8 wt.% steel. However, the wear rates were lowest for the hybrid reinforcement mix of steel and graphite, followed by those containing only steel; while that reinforced with SiC had the highest wear susceptibility. Nonetheless, abrasive wear was the dominant wear mechanism observed in all the composites.