A practical strategy for improving the weldability of ultra-thin Al/Mg sheets by ultrasonic-assisted friction stir welding

In order to enhance the weldable thickness and tensile properties of dissimilar ultra-thin Al/Mg alloy sheets, ultrasonic-assisted friction stir welding (UaFSW) was performed. The addition of ultrasonic produces three benefits. First, a sound joint with smooth surface appearance was achieved. Next, weldable thickness and mixing degree of Al/Mg alloys were improved based on better material flow. Finally, continuous intermetallic compound (IMC) layer in the conventional joint was broken into small pieces, delaying crack propagation. Maximum tensile strength of the UaFSW joint reached 130 MPa, which was much more higher than 102 MPa of the conventional joint. It is concluded that UaFSW has a huge potential to join dissimilar alloys, especially those with the formation of IMCs.