Characterisation studies and mechanical properties of Al7075 composites reinforced with Cr₂O₃ and Fe₂O₃ nanoparticles using squeeze casting technique

This study reports the fabrication and characterisation of Al7075-based nano-sized chromium oxide (Cr₂O₃) and iron oxide (Fe₂O₃) particle-reinforced metal matrix composites by the squeeze casting technique. The main aim of the research was to analyse the effect of double ceramic oxide reinforcement at different weight percentages – 3, 5 and 7 wt-% on the microstructural, mechanical, and tribological properties of the composite material against the unreinforced base Al7075 alloy. Squeeze casting was utilised to provide high-density defect-free castings through pressure application during solidification. Microstructural observations indicated even particle distribution and grain refinement in smaller and moderate levels of reinforcement, whereas SEM fractography indicated a shift in fracture mode from ductile towards brittle with increased reinforcement. Tensile strength and hardness were significantly enhanced with increased reinforcement, with the 5 wt-% showing the best performance. The wear rate was considerably reduced with reinforcement owing to enhanced surface hardness and the development of protective tribolayers. The 7 wt-% reinforcement, there was no significant improvement in properties owing to particle agglomeration and slight porosity increase. The results establish that hybrid Cr₂O₃ and Fe₂O₃ reinforcement enhances load-carrying and wear properties of Al7075 with negligible sacrifice in ductility and density.