Hybrid Friction Stir Welding: The Role of Ultrasonic Vibration and Tool Rotation in Enhancing the Joint Properties

Aluminum-lithium (Al-Li) alloys have gained considerable attention in the aerospace sector due to their superior mechanical properties and strength-to-weight ratio. However, joining these alloys through fusion welding presents challenges including solidification cracking. Friction Stir Welding (FSW) has emerged as a viable solution, offering improved mechanical performance and minimized defects. Recently, ultrasonic vibration-assisted FSW (UVaFSW) has been introduced to further enhance weld quality by refining grain structure and improving plastic flow. This study investigates the impact of UVaFSW parameters, specifically tool rotational speed (TRS) and vibration amplitude (Amp), on the microstructural and mechanical properties of AA2060-T8E30 Al-Li alloy widely utilized in the aviation sector. The experimental analysis reveals that TRS of 800 rpm results in enhanced tensile strength, while higher TRS (1600 rpm) induces excessive heat, leading to grain coarsening and reduced mechanical performance. Additionally, increasing vibration amplitude from 7.5 μm to 22.5 μm significantly improves the welded joints quality. The findings emphasize the potential of UVaFSW in enhancing welding of Al-Li alloy, offering a suitable approach for high-performance aerospace applications.