Microstructural and mechanical characterization of AA6082/SiC/Al2O3 hybrid nanocomposite fabricated by ultrasonic-assisted and vacuum die stir casting

The utilization of aluminium alloys has increased rapidly in past decades due to the increasing demand for lightweight and high-performance materials. Among the popular aluminium alloys, AA6082 is widely favoured for its excellent combination of strength, corrosion resistance, and machinability. To further enhance its mechanical properties without compromising its inherent advantages, hybrid metal matrix composites were developed using various nano particulates as reinforcements. In this current study, the relatively unexplored AA6082-based composite reinforced with nano-sized silicon carbide (SiC) and aluminium oxide (Al2O3) were fabricated through a combination of ultrasonic assisted and vacuum die stir casting. Hybrid reinforcements of nano SiC and Al2O3 were added at varying weight fractions of 0.5 wt%, 0.75 wt%, and 1 wt% each by a two-step stir casting process. The fabricated composites were subjected to detailed microstructural characterization along with mechanical property evaluation through hardness, tensile and compression tests. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to examine the dispersion of reinforcements and the phase composition. Among the composites fabricated, AA6082- 1 wt% SiC and Al2O3 hybrid aluminium matrix nanocomposite (AMNC) exhibited the highest improvements in Vickers hardness, ultimate tensile strength and compression strength, showing increases of 21.92%, 60.78%, and 30.5% respectively, compared to unreinforced AA6082 alloy. The results demonstrated a significant enhancement in mechanical properties with increasing reinforcement content, primarily due to grain refinement, uniform distribution, and effective load transfer confirming the effectiveness of hybrid nano reinforcement and ultrasonic assisted stir casting.