OBRABOTKAMETALLOV Vol. 26 No. 2 2024 technology 2,000 rpm and welding speed of 40 mm/min. However, it should be noted that when the welding speed was reduced to 28 mm/min, a lower surface roughness of 15.16 µm was obtained. ● The microhardness of the joints that underwent shot peening during the UVaFSW welding process showed variation in the welding zones, forming a letter ‘W’ shape. The maximum microhardness value was observed in the WN zone while the minimum was found in HAZ. Additionally, the microhardness values were higher in shot-peened UVaFSW joints compared to conventional FSWed joints. ● Inspection of the shot-peened UVaFSWed joint has shown that the material fusion in the weld nugget was appropriate, there was a flow of pasty material, the joint was free of tunnel defects and voids, and there was a homogeneous distribution of finer grains. This was found to be superior to the conventional FSWed joints. ● All the test specimens for the shot-peened UVaFSWed joints were fractured in the HAZ due to lower microhardness, and it exhibited ductile behavior during fracture. The fractured surface of the shot-peened UVaFSWed joints showed larger, more equiaxed, and shallow dimples, resulting in higher ultimate tensile strength (UTS) and microhardness compared to the conventional FSWed joints. ● The mechanical properties and microstructure observed in the welding zones of shot-peened UVaFSWed joints are superior to those of conventional FSW joints. This study suggests the potential for optimizing the shot-peened UVaFSWed joints of AA7075-T651. References 1. Cetkin E., Çelik Y.H., Temiz S. Microstructure and mechanical properties of AA7075/AA5182 jointed by FSW. Journal of Materials Processing Technology, 2019, vol. 268, pp. 107–116. DOI: 10.1016/j.jmatprotec.2019.01.005. 2. Chinchanikar S., Gaikwad V.S. State of the art in friction stir welding and ultrasonic vibration-assisted friction stir welding of similar/dissimilar aluminum alloys. Journal of Computational and Applied Research in Mechanical Engineering, 2021, vol. 11, pp. 67–100. DOI: 10.22061/JCARME.2021.7390.1983. 3. Arora A., De A., Debroy T. Toward optimum friction stir welding tool shoulder diameter. Scripta Materialia, 2011, vol. 64, pp. 9–12. DOI: 10.1016/j.scriptamat.2010.08.052. 4. Shi L., Wu C.S., Liu X.C. Modeling the effects of ultrasonic vibration on friction stir welding. Journal of Materials Processing Technology, 2015, vol. 222, pp. 91–102. DOI: 10.1016/j.jmatprotec.2015.03.002. 5. Yao Z., Kim G.Y., Faidley L., Zou Q., Mei D., Chen Z. Effects of superimposed high-frequency vibration on deformation of aluminum in micro/meso-scale upsetting. Journal of Materials Processing Technology, 2012, vol. 212, pp. 640–646. DOI: 10.1016/j.jmatprotec.2011.10.017. 6. Siddiq A., El Sayed T. Acoustic softening in metals during ultrasonic assisted deformation via CP-FEM. Materials Letters, 2011, vol. 65, pp. 356–359. DOI: 10.1016/j.matlet.2010.10.031. 7. Liu X.C., Wu C.S. Experimental study on ultrasonic vibration enhanced friction stir welding. Proceedings of the 1st International Joint Symposium on Joining and Welding, Osaka, Japan, 2013, pp. 151–154. DOI: 10.1533/9781-78242-164-1.151. 8. Xu C., Sheng G., Cao X., Yuan X. Evolution of microstructure, mechanical properties and corrosion resistance of ultrasonic assisted welded-brazed Mg/Ti joint. Journal of Materials Science and Technology, 2016, vol. 32, pp. 1253–1259. DOI: 10.1016/j.jmst.2016.08.029. 9. Liu X., Wu C., Padhy G.K. Characterization of plastic deformation and material flow in ultrasonic vibration enhanced friction stir welding. Scripta Materialia, 2015, vol. 102, pp. 95–98. DOI: 10.1016/j.scriptamat.2015.02.022. 10. Amuda M.O.H., Mridha S. Comparative evaluation of grain refinement in AISI 430 FSS welds by elemental metal powder addition and cryogenic cooling. Materials and Design, 2012, vol. 35, pp. 609–618. DOI: 10.1016/j. matdes.2011.09.066. 11. Hatamleh O., Hill M., Forth S., Garcia D. Fatigue crack growth performance of peened friction stir welded 2195 aluminum alloy joints at elevated and cryogenic temperatures. Materials Science and Engineering A, 2009, vol. 519, pp. 61–69. DOI: 10.1016/j.msea.2009.04.049. 12. Hatamleh O., Mishra R.S., Oliveras O. Peening effects on mechanical properties in friction stir welded AA2195 at elevated and cryogenic temperatures. Materials and Design, 2009, vol. 30, pp. 3165–3173. DOI: 10.1016/j. matdes.2008.11.010. 13. Khorrami M.S., Kazeminezhad M., Miyashita Y., Saito N., Kokabi A.H. Influence of ambient and cryogenic temperature on friction stir processing of severely deformed aluminum with SiC nanoparticles. Journal of Alloys and Compounds, 2017, vol. 718, pp. 361–372. DOI: 10.1016/j.jallcom.2017.05.234.
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