Structure property correlations of vacuum assisted squeeze cast AA5085-SiC-Si3N4 hybrid composites

Hybrid aluminium matrix composite has attracted significant attention for high-performance structural and tribological applications owing to its high strength-to-weight ratio and multifunctional properties. Nevertheless, the monolithic AA5085 alloy has inferior hardness and mechanical properties, making it prone to wear and corrosion and limiting its use in hostile operating conditions, which is a major challenge. This study is novel because it has demonstrated synergistic multi-property enhancement through controlled hybrid reinforcement and defect-suppressed processing. In this work, hybrid composites comprising AA5085 and reinforced with SiC (2-6 wt.%) and a constant 2 wt.% Si 3 N 4 were prepared by vacuum-assisted squeeze casting to reduce the porosity and distribute particles evenly. Further, its microstructural evolution (SEM, EDS, XRD), mechanical behaviour (hardness, tensile, flexural, compressive, and impact), corrosion, and tribological characteristics have been characterised and compared with those of the cast AA5085 alloy. Microstructural characterisation affirmed the presence of refined grains and effective interfacial bonding, which contributed to enhanced hardness (20.9%), tensile (24.42%), compressive (41.9%), flexural (30.6%), and impact strengths (42.1%) of AA5085 by increasing load transfer and interfacial bond strength. These improvements were accompanied by a gradual decrease in ductility because of limited matrix plasticity. The reinforcing additions further enhanced corrosion resistance by forming protective oxide-rich surface films of Al 2 O 3 and Al(OH) 3 and by providing a barrier to the ingress of chloride ions. Wear experiments showed a large decrease in the wear loss% with the base alloy due to the load-bearing effect of SiC, development of a stable mechanically mixed layer, and enhanced interfacial integrity caused by the Si 3 N 4 . These findings illustrate an improved hybrid reinforcement technique for creating high-performance, lightweight aluminium composites suitable for demanding structural and tribological environments.