Synergistic effects of boron carbide and eggshell particles on mechanical and tribological properties of ultrasonic-assisted stir cast aluminium alloy based composites

Abstract

Aluminium matrix composites are in high demand for their lightweight nature and favourable properties, yet issues like high thermal expansion, low microhardness or high cost often challenge them. To address these limitations, the integration of sustainable, cost-effective reinforcing agents that can enhance hardness and wear resistance can be explored, as this can broaden the application scope of these composites across various industries. The present study fabricates aluminium matrix composites with aluminium alloy (AA6063-T6) as a matrix and different wt.% (0%, 2% and 4%) of micro-sized eggshell (ES) and boron carbide (B4C) particles as reinforcements through ultrasonic-assisted stir-casting. Analysis of microstructure, mechanical and tribological properties of the fabricated composites are done and compared to those of the as-cast base alloy. Results from optical and scanning electron microscopy (SEM), together with energy-dispersive X-ray spectroscopy (EDS) analysis, revealed the uniform distribution of reinforcements in all three composites. X-ray diffraction (XRD) indicated the formation of several compounds in each composite. Among all, the as-cast base alloy exhibited the lowest porosity at 0.48%. The AA6063-T6/B4C composite demonstrated the highest hardness, with an increase of 46.08%, while the AA6063-T6/ES/B4C composite achieved the highest tensile strength, showing a 62.28% improvement compared to the as-cast base alloy. As the load increased from 20N to 60N, the wear rate of the reinforced composites rises while the coefficient of friction decreased, with the AA6063-T6/B4C composite showing the highest wear resistance.