Investigating the Microstructural and Wear Properties of Graphene-Reinforced Aluminium 6061-T6 Surface Composites Fabricated Using Friction Stir Processing

Friction Stir Processing (FSP) is a promising solid-state technique for the fabrication of surface composites with improved mechanical and tribological properties. In the present work, graphene-reinforced AA6061-T6 surface composites were fabricated using the groove filling method followed by FSP. The effects of tool rotational speed (1000 and 1200 rpm) and graphene volume fraction (15, 20, and 25 vol.%) on the microstructure and wear behavior of the composites were investigated. The distribution of graphene was found to be strongly dependent on the processing parameters. Improved material flow and more uniform reinforcement dispersion were achieved at the higher rotational speed of 1200 rpm, whereas higher graphene content resulted in localized agglomeration and defect formation in some specimens. The wear behavior showed significant dependence on both rotational speed and graphene content. Among the samples processed at 1000 rpm, the specimen containing 20 vol.% graphene exhibited lower wear compared to the other conditions. For the specimens processed at 1200 rpm, the composite reinforced with 25 vol.% graphene demonstrated the lowest wear depth and the best wear resistance. The enhanced tribological performance was attributed to the combined effects of grain refinement, improved graphene dispersion, and the formation of a protective graphene-rich tribolayer during sliding. Although variations in the coefficient of friction were observed, wear resistance was found to be more strongly influenced by microstructural integrity and reinforcement distribution.