Influence of Nanometric and Micrometric Reinforcement on Machining of Powder-Forged Al-7075/Y2O3 Composites

This investigation reports the influence of vol.% and size (micrometric/nanometric) of the reinforcement particles on machinability of near-full-density (> 99% relative density) powder-forged Al-7075/Y₂O₃ composites. The composites were processed with 0.1-3. vol% nanometric and 1-10 vol.% micrometric reinforcement and studied in artificially aged (T₆) and solutionized conditions. Drilling was performed without applying cutting fluid at 140 rpm rotational speed and 0.12 mm/rev feed rate to produce through holes. Cutting force components (F_t and F_c) and machined surface roughness (R_a) were considered as machinability criteria. The results showed that the reinforcements influence F_t and F_c in both conditions correspondingly as they cause structural alterations and affect composites’ hardness. Nevertheless, the reinforcements’ effects in T₆ were not as prominent as in solutionized condition. In the former condition, the hardness of the alloy matrix due to the formation of precipitates overrides the hardness due to structural alterations caused by reinforcements. Pull-out of secondary reinforcement particles was observed while machining. Besides the composites’ hardness, abrasion of the pulled-out reinforcement particles and stuck-up debris of the broken chips on the freshly machined surface governs its roughness. Only a few earlier studies have opted for Y₂O₃ reinforcement and processed Al-7075/Y₂O₃ composites by powder forging. Further, machining of Al-7075/Y₂O₃ composites in solutionized and T₆ conditions has been scarcely investigated, and their machinability has been hardly ever analyzed with respect to reinforcement parameters, size, and vol.%.