Effect of ultrasonic vibration on the friction stir weld quality of aluminium alloy

A novel variant of friction stir welding process,referred as ultrasonic vibration enhanced friction stir welding,is developed to transmit ultrasonic vibration energy directly into the localized area of the workpiece near and ahead of the rotating tool.Experiments are conducted on 6061-74 aluminium alloy plates by this new process and the conventional friction stir welding process,respectively.The morphology and macrograph of the welds under both conditions are observed and contrasted.The experimental results show that ultrasonic vibration enhanced friction stir welding can improve the weld formation quality and increase the welding efficiency.And it just needs a smaller axial downward force.Because that the added action of ultrasonic vibration energy may enhance the localized softening extent and the plastic flow around the tool.In addition,it also improves the mechanical properties of the welded joints.