Comparative analysis of reinforcement addition techniques on fabricated hybrid surface composite of AA7075-T651/WC/BN through friction stir processing

In the present work, three reinforcement addition techniques such as the slot method (SM), hole method (HM), and zig-zag hole method (ZZHM), are selected to make the hybrid surface composite of AA7075-T651/BN/WC through FSP. The comparative assessment of each method is thoroughly assessed through microstructure, mechanical, and tribological characteristics. Material flow, particle spreading, zone development and phase formation were examined using optical microscopy (OM), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Furthermore, the microhardness and wear characteristics were measured and compared. Based on the findings, ZZHM reveals enhanced material flow and more even particle spreading in the nugget zone than SM and HM. The higher grain refinement and excellent interfacial bonding without any reaction between AA7075-T651 and reinforcement particles (BN and WC) are due to higher DRX and severe plastic deformation (SPD) caused by the tool in ZZHM. The composite made with ZZHM had greater hardness and wear resistance due to the reduction in clusters, even the spreading and lubricating effect of particles and a significant reduction in grain size. This study revealed that the ZZHM is superior to the SM and HM for adding reinforcement and fabricating the hybrid surface composite.