Microstructure and Mechanical Properties of Hybrid Pure Al/B4C/Microsilica Composites Produced by Ultrasonically Assisted Stir Casting

This study explores the fabrication and characterization of hybrid aluminum matrix composites reinforced with boron carbide (B4C) and microsilica, produced via ultrasonically assisted stir casting followed by T6 heat treatment. Pure aluminum was selected as the base matrix to evaluate the combined effects of B4C and microsilica reinforcements. Microstructural analyses showed that ultrasonic treatment effectively dispersed nanoparticles, reduced agglomeration, and enhanced particle–matrix interfacial bonding. T6 heat treatment further refined the grain structure through Zener pinning and promoted the formation of reaction layers at particle interfaces. Mechanical testing revealed that Al/B4C composites provided the highest strength and hardness, while Al/microsilica systems retained superior ductility. The hybrid Al/B4C/microsilica composites demonstrated a balanced combination of yield strength (38.6 MPa), ultimate tensile strength (82.6 MPa), and elongation (35.2%), confirming a synergistic strengthening–toughening effect. These results highlight the potential of Al/B4C/microsilica hybrid reinforcements to optimize the trade-off between strength and ductility in aluminum-based composites.