Impact of Hard and Soft Reinforcements on the Microstructure, Mechanical, and Physical Properties of the Surface Composite Matrix Manufactured by Friction Stir Processing

This work studies the effect of incorporating a mix of reinforcement particles of a hard and soft nature on the microstructure and mechanical and physical properties of a high-strength aluminum alloy, AA7075. A friction stir processing technique was used for compositing the surface of this alloy. The vanadium carbide (VC) was selected to be the hard reinforcement, while the boron nitride (BN) and graphene nanoplates (GNPs) were chosen as soft reinforcements. Mono VC, hybrid reinforcements combined of 50 vol.% VC and 50 vol.% BN, and triple reinforcements combined of 33.4 vol.% VC, 33.3 vol.% BN, and 33.3 vol.% GNPs were used for producing the composites. Intensive grain refinement was observed, 930%, in the composite with triple reinforcements. The microhardness and the ultimate compressive strength were improved and reached b0, 29%, respectively, in composites that contained GNPs. The thermal properties were significantly improved, and the coefficients of thermal expansion (CTE) and thermal conductivity decreased to 88% and 15%, respectively. The composite’s electrical conductivity was decreased by 58% with triple reinforcements.