Influence of graphene reinforcement on the mechanical and tribological characteristics of AA2198T8–AA2024T3 friction stir welded joints

This paper discusses the short-coming of decreased mechanical and tribological actions in dissimilar friction stir welded (FSW) joints of precautionary hardened aluminum alloys, especially AA2198-T8 and AA2024-T3, due to thermal softening and microstructural instability in the stir zone. Its main objective is to examine the impact of graphene nanoplatelet reinforcement on mechanical, tribological, and dynamic mechanical behavior of similar and dissimilar FSW joints. In this study, controlled FSW parameters were used to produce similar (AA2198+AA2198, AA2024+AA2024), dissimilar (AA2198+AA2024) and graphene-reinforced dissimilar joints (0.3 wt.%). Systematic characterization of joints was done by tensile testing, hardness mapping, pin-on-disc wear testing, and dynamic mechanical analysis (DMA), and SEM/EDS microstructural analysis. The results demonstrate that graphene reinforcement significantly enhances joint performance, with the dissimilar reinforced joint exhibiting a yield strength of ∼398 MPa, ultimate tensile strength of ∼505 MPa, and ∼99% joint efficiency. Improved hardness (∼149 HV), reduced specific wear rate (∼4.83 × 10 -4 mm 3 /N·m), and lower coefficient of friction (∼0.34) were observed due to grain refinement, dislocation pinning, and effective load transfer. DMA results further revealed enhanced stiffness retention, higher damping viscosity, and improved thermal stability of the reinforced joint. Fractographic analysis confirmed predominantly ductile failure with refined microstructural features. Overall, the study establishes graphene reinforcement as an effective strategy to overcome weld-zone softening and enhance the multi-functional performance of dissimilar FSW joints for advanced structural applications.