Dry sliding wear behavior of Al5Cu-B4C-Gr hybrid composites fabricated by hybrid microwave heating

In this study, Al5Cu matrix hybrid composites reinforced with varying ratios of boron carbide (B4C) and graphite (Gr) were produced via powder metallurgy, followed by hybrid microwave sintering. The effects of B4C and Gr contents on the physical, microstructural, mechanical, and dry sliding wear behavior of the composites were systematically evaluated. Powder characterization revealed that irregular Al, spheroidal Cu, angular B4C, and lamellar Gr particles formed a heterogeneous initial powder architecture that influenced densification and the distribution of reinforcement. After sintering, all samples exhibited increased relative density and reduced porosity. The highest sintered density and sinterability value (37.26%) were obtained for AC1, which had the lowest total reinforcement content. XRD analysis confirmed the presence of the Al matrix, B4C, Gr, Al2Cu, Al2O3, and Al7Cu2Fe phases. SEM-EDX results supported the retention of B4C and Gr within the matrix and confirmed the local Al-Fe-Cu enrichment associated with Al7Cu2Fe-type phase formation. The highest Brinell hardness (65.23 HB) and microhardness (88.30 HV0.05) were observed for AC2, owing to its higher B4C content and sufficient densification. In contrast, the lowest average coefficient of friction was measured for AC3 (0.5040), while the lowest specific wear rate was obtained for AC4 (1.9079×10-3 mm3/Nm). These results show that wear resistance was governed not by hardness alone, but by the combined load-bearing effect of B4C, the lubricating action of Gr, and the microstructural state developed during hybrid microwave sintering.