OBRABOTKAMETALLOV technology Vol. 26 No. 2 2024 threaded tool on a universal milling machine. The two plates to be welded originally had a rectangular shape and were deburred. The faying edges of the plates were machined into a smooth surface and cleaned with acetone. The ultrasonic vibrations generated by the ultrasonic transducer propagated through an amplitude transformer to expand the amplitude and focus the energy at the weld line of two plates. This energy was transmitted to the localized workpieces near and in advance of the FSW tool by a sonotrode. An output power of 1.2 kW and an ultrasonic vibration frequency of 20 kHz were used in the welding process. In the absence of a load, a vibration amplitude of 24 µm was used. The sonotrode was placed at an angle of 45° to the plane of the workpiece and at a distance of 20 mm from the FSW tool. a b Fig. 2. Schematic view (a), Actual experimental setup (b) The tool with translational and rotational motions provides thermo-mechanical action along the welding path. The conical threaded tool pin profile with flat shoulder made of tool steel type H13 is depicted in Fig. 3. The axial load on the work surface is transmitted by the tool shoulder. The plasticized material is transferred in to the weld pool by the pin. Tables 1 and 2 represent the chemical composition of the tool and the workpiece material respectively. In the present study, the shot peening process is selected as a postweld treatment. The experimental set-up and parameters of the shot peening are depicted in Fig. 4. The microstructure of the shot-peened UVaFSWed joints at different regions of the weld and the material flow in the WN were examined using SEM images. The mechanical properties of the joint, such as UTS, microhardness in WN, thermo-mechanically affected heat zone (TMAZ), HAZ, base metal, and surface roughness (SR), are inspected considering the influence of process variables. The shot peened UVaFSWed joint transverse UTS, and joint efficiency were evaluated for all the joints obtained at different process parameters. The tensile test was performed on a universal testing machine according to the ASTM E8 standard. Fig. 5, a, b shows a diagram of cutting a plate made of aluminum alloy AA7075-T651 to obtain a test specimen and a tensile test specimen, respectively. The microhardness at WN, TMAZ, HAZ, and BM was measured using Vicker’s microhardness tester in accordance with ISO6507 standard by the means of diamond indenter (136o) through a load of 100 grams and an indentation time of 20 seconds. An average SR, measured at the start, middle, and end of the weld, was obtained. Fig. 3. Conical threaded pin type tool (All dimensions are in mm)
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