Structural and Physical Property Enhancement in Al 7075–Boron Carbide–Zirconium Dioxide Hybrid Nano Composites

The Aluminum Metal Matrix Composites (AMMCs) continue to attract substantial research interest for high-performance locomotive, aerospace, and defense structures due to their superior specific strength, stiffness, and tribological behavior. The present investigation aims to enhance the mechanical response of Al 7075 by hybrid augmentation with ceramic particulates. Boron carbide (B4C), known for its high hardness and modulus, was incorporated at a constant weight fraction, while zirconium dioxide (ZrO2), a toughening ceramic with high thermal stability, was introduced in varying weight percentages to evaluate its incremental contribution to composite performance. Hybrid composites were synthesized via the Stir Casting Method (SCM), selected for its capability to disperse ceramic reinforcements uniformly in the molten matrix through controlled vortex formation. Process parameters such as stirring temperature, stirring speed, and holding time were systematically regulated to minimize particle clustering, interfacial porosity, and wetting inconsistencies. Mechanical characterization comprised tensile testing, compression testing, and Brinell hardness evaluation in accordance with ASTM standards. Results indicated that hybrid reinforcement significantly enhances load-bearing capability and resistance to deformation. The composite containing Al 7075 + 3 wt. % B4C + 15 wt. % ZrO2 achieved the highest tensile strength of 192 MPa, compared to 137 MPa for the monolithic alloy, demonsrating a 40 % improvement. Similar trends were observed in compressive strength and hardness, attributed to particle-matrix interfacial strengthening, Orowan looping, dislocation pile-up at reinforcement boundaries, and microstructural refinement induced by ceramic additions. To identify the most influential processing parameters and optimize the mechanical response, the Taguchi L9 orthogonal array was employed. Signal-to-noise analysis confirmed that reinforcement ratio and stirring temperature were the dominant factors affecting property enhancement. The optimized parameter set yielded composites with superior mechanical performance and reduced variability. Overall, the findings establish that B4C-ZrO2 hybrid-reinforced Al 7075 composites fabricated via SCM are promising candidates for next-generation lightweight structural components demanding high strength, reliability, and thermal resilience.