Enhanced Mechanical Performance of Al7075/ 3–9 wt % SiC and 2 wt % Al ₂ O ₃ Hybrid Composites Through T6 Heat Treatment

The applications of aluminium metal matrix composites (AMMCs) using Al7075 as the base alloy are increasing in the automobile and aerospace industries due to their superior strength‐to‐weight ratio. Al7075, being a heat‐treatable alloy, offers scope for enhancing mechanical properties through suitable reinforcement and heat treatment. In this study, hybrid AMMCs were fabricated using Al7075 alloy reinforced with silicon carbide (SiC) and aluminium oxide (Al ₂ O ₃ ) particles through the stir casting process. The stir casting process involves melting preheated Al7075 alloy at 650°C and further heating it to 780°C for complete liquefaction. Preheated reinforcements (650°C) are then added and stirred thoroughly for uniform blending. Subsequently, 2 g of magnesium powder is introduced into the slurry to improve wettability. After solidification, the material is removed from the mould to produce samples using a wire‐cut electrodischarge machine. SiC was added in varying proportions of 3, 5, 7 and 9 wt %, while Al ₂ O ₃ was maintained at a constant 2 wt % for all samples. The T6 heat treatment of the samples involved solutionizing at 530°C, holding time for 8 h, ageing at 165°C for 8 h and cooling by water quenching. Mechanical and metallurgical properties were examined for both as‐cast and heat‐treated (T6) composites. The results revealed that the inclusion of SiC and Al ₂ O ₃ significantly improved the tensile strength and hardness of the composites compared to the base alloy. The heat‐treated specimens exhibited superior performance compared to as‐cast samples, achieving a maximum tensile strength of 553.1 MPa (70% increment) and hardness of 204.5 VHN (71.8% increment), compared to 325 MPa and 119 VHN for the as‐cast samples. SEM micrographs confirmed uniform dispersion of reinforcements and refined grain structures in heat‐treated composites. The strengthening mechanisms in metal matrix composites mainly include load transfer, Hall–Petch strengthening and Orowan strengthening. Strengthening occurs by load transfer from the ductile matrix to the hard reinforcement particles, Hall–Petch strengthening by an increase in the number of grain boundaries to obstruct dislocations and Orowan strengthening, in which dislocations form loops around reinforcements, obstructing dislocation movement. The developed hybrid AMMCs demonstrate excellent potential for structural applications in the aerospace and automotive sectors.