Investigation of the mechanical and tribological properties of Al7075-Si3N4-graphene and Al7075-B4C-graphene hybrid composites

In this study, Al7075-Si3N4-graphene and Al7075-B4C-graphene composite structures were produced by the powder metallurgy and induction hot pressing methods. Al7075 matrix was reinforced with 1, 3, 6, 9, 12% Si3N4, 1, 3, 6, 9, 12, 15, 30% B4C and 0.1, 0.3, 0.5% graphene. The effects of reinforcement ratio and heat treatment type (sintering and induction hot pressing) on the microstructure, mechanical (density, porosity ratio, Vickers hardness, compressive strength) and tribological properties (wear rate, mass loss and friction coefficient) of composites were investigated. As a result of the tests carried out, the densest microstructure and the best mechanical and tribological properties were reached in the induction hot pressed Al7075-9Si3N4 composite structure among the Al7075-Si3N4 composites For this reason, graphene was reinforced to the Al7075-Si3N4 composite structure in different ratios. Among the Al7075-9Si3N4-graphene composites, the highest density (2.68 g/cm3), Vickers hardness (238 HV), compressive strength (378 MPa) and lowest wear rate (0.00016 mm3/Nm), mass loss (0.0021 g) induction hot pressed Al7075-9Si3N4-0,1graphene composite structure was obtained. Among the Al7075-B4C composites, the densest microstructure and the best mechanical and tribological properties were obtained with 30%B4C content. For this reason, graphene was reinforced to the Al7075-B4C composite structure in different ratios. Among the Al7075-30B4C-graphene composites, the highest density (2.64 g/cm3), Vickers hardness (256 HV), compressive strenght (526 MPa) and the lowest wear rate (0,000076 mm3/Nm), mass loss (0,001 g) were obtained in the induction hot pressed Al7075-30B4C-0.1graphene composite structure. However, the mechanical and tribological properties of composites deteriorated due to agglomeration of graphene above 0.1% graphene amount. As a result, it was determined that the mechanical and tribologic certain amount of Si3N4/B4C and graphene to the Al7075 matrix up to a certain content. In addition, the porosity in the microstructure was reduced by the effect of the induction hot pressing process. Accordingly, it was determined that the mechanical and tribological properties of the composite improved.