Wear and microhardness behaviors of AA7075/SiC-BN hybrid nanocomposite surfaces fabricated by friction stir processing

Abstract

The wear resistance and microhardness behavior of hybrids consisting of wrought aluminum alloy AA7075 with different volume fractions of SiC and BN nano-powders were investigated experimentally. The surfaces of the hybrid nanocomposites were fabricated by friction stir processing (FSP). The microstructure of the reinforcement nano-powders and fabricated nanocomposite surface were examined using scanning electron microscopy (SEM) and high-resolution polarized optical microscopy. The wear resistance and microhardness tests were performed on the specimens before and after the fabrication process. The AA7075 showed a large grain size with an average of 178 μm, while the hybrid composites of AA7075/SiC-BN showed finer grains with an average size of 8 μm due to the FSP parameters. Additionally, a good nano-particle surface dispersion was clearly visible with nearly no voids. The wear resistance results showed that the addition of SiC and BN nano-particles increased the fabricated nanocomposite surface wear resistance by 53-61%. It was also noted that the wear resistance rate had a clearly inverse relationship with the increasing mass fraction of the nano-particles. The presence of SiC and BN nano-particles also increased the hardness by an average of 45%. The volume fraction of the reinforced nanoparticles had a significant impact on the mechanical and wear properties of the fabricated hybrid nanocomposite surfaces.