Development of sustainable AA6061 hybrid composites reinforced with silica sand and copper for high-performance applications

This study investigates the fabrication and mechanical enhancement of AA6061-based hybrid metal matrix composites (HMMCs) reinforced with silica sand and copper particles. Two composite variants, AA6061–2SiO₂–4Cu (AA2S4C) and AA6061–4SiO₂–2Cu (AA4S2C), were developed with a total reinforcement content of 6 wt.% using the stir casting technique. A novel low-temperature thermomechanical treatment (LTMT), comprising solution treatment, cold rolling, and isothermal ageing at 100 °C and 180 °C, was employed to improve the mechanical properties. Microstructural analysis confirmed uniform dispersion of reinforcements, while Brinell and micro-Vickers hardness tests demonstrated significant improvements in hardness. The AA4S2C composite, with a higher silica sand content, exhibited superior mechanical properties due to the higher hardness and volume fraction of ceramic reinforcement. LTMT-processed AA4S2C achieved a 132 % increase in peak hardness and a 99 % rise in ultimate tensile strength (UTS) compared to as-cast AA6061. Fractographic analysis revealed a mixed failure mode dominated by ductile fracture, indicating improved toughness. The integration of naturally sourced silica sand and copper, combined with LTMT, offers a cost-effective and sustainable route to producing high-performance composites. These findings highlight the potential of AA6061-SiO₂-Cu HMMCs for demanding applications in aerospace, automotive, and structural engineering sectors.