Influence of various tool shoulder design on hybrid surface composite of AA7075-T651/SiC/graphene through friction stir processing

Abstract

ABSTRACT In the recent work, tool shoulder designs such as flat shoulder (TFS), kurl shoulder (TKS), scroll shoulder (TSS), and knurling (TKNS) were creatively designed to improve the surface properties. The AA7075/SiC/Graphene hybrid surface composites were fabricated through friction stir processing using different shoulder designs. The influence of shoulder designs on microstructure, mechanical, tribological, and corrosion properties were examined. The material characterizations such as macrostructure, microstructure, particle dispersion, and elemental analysis were studied through optical microscopy and field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy. The current study found that the dispersion of SiC and graphene particles inside the matrix fabricated by the TSS tool design was more uniform due to the tool shoulder feature, leading to improved material flow during stirring. The sample fabricated using the TSS tool displayed higher grain refinement, the smallest grain size, which was 3.5 μm. The TSS design effectively eliminated the cluster formation and obtained a defect-free composite resulting in greater hardness (197 HV), lower wear resistance (0.0038 mm3/m) and higher corrosion resistance (– 0.650 mV) compared to other tool designs. However, the lowest values of hardness, wear rate, and corrosion resistance were obtained by TFS design.