Nanotechnology

Indentation hardness

Nanoparticle

Composite material

Metallurgy

Materials science

Scanning electron microscope

Friction stir processing

Boron carbide

Alloy

Carbide

Microstructure

Journal of Materials Research and Technology

In this study, the fabrication of hybrid metal-matrix-surface composites (HMMSC) through the friction stir process (FSP) was investigated, where hexagonal boron nitride (HBN) was used as a continuously reinforced nanoparticle to improve the tribological behavior of AA7075 aluminum alloy. At the same time, silicon carbide (SiC), tantalum carbide (TaC), and niobium carbide (NbC) nanoparticles were used as secondary reinforced particles that exhibited improved resistance to deformation at elevated temperatures, greater chemical stability, and grain growth control. Hybridization was performed by mixing the same percentage of each element with the hBN nanoparticles before depositing them on the surface of AA7075 aluminum alloy. The presence of reinforcing particles was observed using a scanning electron microscope (SEM), and excellent bonding between the reinforcing elements and the AA7075 aluminum alloy was also observed. Observation of the microstructure of the hybrid composites revealed that the reinforcing nanoparticles were uniformly distributed over the stirred zone, with no evidence of an undesirable strong cluster effect. The grain refinement reached a 4000% reduction with respect to base alloy for the hybrid AA7075/BN_TaC composite matrix. The mechanical properties of the optimal hybrid AA7075/BN_TaC, including compressive strength and microhardness, improved by 26.5% and 40%, respectively, compared to the base alloy. In addition, the presence of hexagonal boron nitride nanoparticles significantly improved the wear resistance, and the wear rate was reduced by 14–24 times.

Improvement of the microstructure and mechanical properties by hybridizing the surface of AA7075 by hexagonal boron nitride with carbide particles using the FSP process