TWI

With regard to the capability of ultrasonic vibration enhanced friction stir welding (UVeFSW) to improve weld formation quality as well as the microstructure and mechanical properties of the welded joints, experiments were undertaken to clarify the underlying mechanism by measuring tool torque and thermal cycles during the welding of AA 2024-T4 (Al, 4.78%Cu, 1.61%Mg, 0.64%Mn) alloy sheets (thickness 2.9 mm). The UVeFSW set-up comprised an ultrasonic vibration system (ultrasound generator, transducer, amplitude transformer and vibration tool head) and a conventional FSW machine. Comparative FSW and UVeFSW trials were conducted using the same set of process parameters (welding speed, tool rotational speed and plunge depth). Microstructure was observed by optical microscopy and inner defects were examined by radiography. Mechanical properties were characterised by microhardness distribution measurements and tensile tests. The enhancement of material plastic flow by integration of ultrasonic vibration into the FSW process is discussed.

10th International Symposium, 20-22 May 2014, Session 9A: Techniques III, Paper 01