Microstructural evolution, mechanical performance and ANFIS-based optimization of friction stir welded AA7075/B ₄ C/BFS hybrid composites using cryogenically treated tools

Friction stir welding (FSW) of non-ferrous hybrid metal matrix composites have been of specific research interest due to the challenges encountered in joining process of compositional heterogeneity of composites. In current study 15 wt.% boron carbide and 8 wt.% blast furnace slag (BFS) reinforced Aluminum AA7075 hybrid composites were developed through stir casting route, and the composite plates were joined through FSW under varying process parameters (tool type, traverse speed and rotational speed). The composite joints were evaluated for mechanical strength and achieved the highest 292.61 MPa strength in tension. Also, nugget hardness, 168.45 HV _0.1 achieved using a threaded cylindrical tool under optimal welding condition. Microstructure study using SEM showed refined equiaxed grains in the nugget zone affirming severe plastic deformation and dynamic recrystallization of the matrix. Additionally, EDS confirmed the successful dispersion and even distribution of reinforcements. Moreover, to identify the process parameters for achieving maximum tensile strength and hardness an adaptive neuro-fuzzy interface system (ANFIS) was developed. The proposed model predicted a maximum UTS of 312.81 MPa at 1290 tool rpm and 13.5 mm/min traverse speed. Furthermore, a maximum micro-hardness of 177.12 HV was achieved at 1278.12 tool rpm and 8.37 mm/min traverse speed. Confirmatory test for the predicted response in ANIFIS showed minimal deviation further validating the accuracy and robustness of the developed model.