Synergistic effects of sustainable SiO₂ nanoparticle reinforcement and Sr modification on the microstructure, mechanical performance, and tribological behavior of ADC12 hybrid composites

Abstract

This study developed a sustainable ADC12 hybrid composite reinforced with SiO₂ nanoparticles and modified with Sr to improve its mechanical and tribological performance. The SiO₂ reinforcement, derived from silica-rich agricultural and industrial waste, provides an environmentally sustainable route for converting low-value waste into value-added engineering materials, thereby reducing environmental impact while improving resource utilization. A ball milling-assisted stir casting process was employed to achieve uniform nanoparticle dispersion and controlled solidification. The combined addition of SiO₂ and Sr refined the microstructure, reducing the secondary dendrite arm spacing (SDAS) from 26.7 to 10.8 μm and transforming eutectic Si from coarse acicular plates into a uniformly distributed fibrous morphology at 0.075 wt% Sr. As a result, the optimum composite exhibited a hardness of 129.4 HV, ultimate tensile strength of 297.9 MPa, and impact energy of 9.8 J/cm². Wear performance also significantly improved, with lower wear loss and a reduced, more stable coefficient of friction. Fractographic and wear analyses revealed a transition from brittle fracture and severe abrasive wear to ductile-dominated fracture and predominantly mild abrasive wear. The enhanced performance arises from the combination of homogeneous SiO₂ nanoparticle dispersion and Sr-induced eutectic Si refinement, which strengthen the matrix, suppress crack initiation, and improve resistance to material removal during sliding. The developed sustainable ADC12 hybrid composite shows considerable potential for lightweight automotive and engineering applications, including gearbox housings, transmission covers, brackets, and other wear-resistant structural components requiring enhanced mechanical properties and improved wear resistance.