Investigation of Effect of Al₂O₃ and SiC on Sintering and Mechanical Properties of Hybrid Al–Based Composites

Abstract

In this research work, Al–SiC (8 wt.%)–Al₂O₃ (2 wt.%) and Al–SiC (6 wt.%)–Al₂O₃ (4 wt.%) bulk composites were synthesized via mechanical alloying and spark plasma sintering at 550 °C and 50 MPa for and 15 min hold. After consolidation, bulk samples did not exhibit any new peaks compared to powder samples, as indicated by XRD patterns. The hardness of the sintered samples was analyzed by a Vickers microhardness tester at 1 N for 20 s hold, and the wear resistance of the samples was studied by fretting wear test at 20 N and 30 N loads. The consolidated samples exhibited Vickers microhardness of 1.5 ± 0.5 GPa and 1.4 ± 0.35 GPa for the two compositions sintered for 10 min hold. When the holding time increased to 15 min, the hardness values decreased to 1.35 ± 0.45 GPa and 1.34 ± 0.25 GPa, respectively. The wear volume losses were higher at 30 N load compared to 20 N load due to higher deformation and formation of a rough surface in the sample, leading to the sample's breaking. The bulk samples of the two compositions sintered for 10 min hold exhibited compression strengths of 492 and 476 MPa, respectively. The strength decreased to 482 and 467 MPa, respectively, when the sintering time was increased to 15 min. The decrease in hardness and compressive strength values can be attributed to increased grain size at a higher holding time. The fracture surface exhibited ductile and brittle fracture modes in the Al matrix and reinforcement phases.