Influence of profile-edge geometry on Yttria-Stabilized Zirconia reinforced AA6061 friction stir welds

In the current study, the effects of edge profile configuration and reinforcement with Yttria-Stabilized Zirconia (YSZ) particles on the microstructure, crystallographic texture, and mechanical properties of friction stir welded AA6061-T651 aluminum alloy joints are investigated. A novel profile-edge joint configuration is employed to improve material flow and particle dispersion in friction stir welding, and is compared with a conventional straight-edge joint configuration. Electron Backscattered Diffraction (EBSD) analysis showed that the profile-edge configuration results in better microstructural refinement of the joint, with an average grain size of 6.6 μm compared with 8.4 μm for the straight-edge joint. Moreover, the amount of high-angle grain boundaries increases from 40.1% to 46.3% due to improved recrystallization. Texture analysis has shown that shear texture components are more pronounced in the profile-edge joint, where the maximum texture intensity is 13.6 times that of a random distribution. Microanalysis of the profile-edge joint using Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDX) showed that yttria-stabilized zirconia particles were successfully incorporated into the stir zone with a relatively uniform distribution. Phases α-Al, Mg ₂ Si, Al ₅ FeSi, zirconia, and yttria-stabilized zirconia have been identified by X-Ray Diffraction (XRD) analysis. The profile-edge configuration resulted in an improved hardness of up to 105 HV, compared with 101 HV for the straight-edge configuration. The mechanical properties are considerably improved in the profile-edge joint, with an ultimate tensile strength of 348 ± 12.9 MPa, a yield strength of 311 ± 10.4 MPa, and an elongation of 12.8 ± 2.5%, resulting in a joint efficiency of 92–95%. Fractographic analysis indicates a ductile fracture with evenly distributed dimples.