Comparative evaluation of conventional friction stir welding and ultrasonic vibration-assisted friction stir welding techniques

Enhancing joint strength in aluminium alloys remains a critical challenge for industrial applications. Friction stir welding (FSW) is a solid-state welding process that offers superior weld quality compared to fusion methods. However, further advancements are needed, particularly for high-performance alloys like third-generation Al-Li. To address this, ultrasonic vibration-assisted FSW (UVaFSW) has been explored as a potential enhancement. This study compares the mechanical and microstructural properties of AA2060-T8-E30 joints produced by FSW and UVaFSW. Key process parameters, including tool traverse speed and ultrasonic vibration amplitude (7.5 µm and 22.5 µm), were varied to assess their influence on weld quality. Mechanical performance was evaluated through tensile testing and Vickers microhardness, while microstructural characteristics were examined using optical microscopy and SEM. The results demonstrated that UVaFSW significantly improved material flow, reduced asymmetry in the thermo-mechanically affected zone (TMAZ), and refined the grain structure. Consequently, the ultimate tensile strength increased by 16.6 % and 31.8 % at 7.5 µm and 22.5 µm amplitudes, respectively, and elongation reached 11 %, nearly three times that of FSW. Furthermore, UVaFSW produced finer grains and more uniform precipitate distribution. Therefore, UVaFSW emerges as a promising technique for enhancing weld quality in advanced Al-Li alloys for demanding engineering applications.