Ultrasonic vibration-induced thinning of intermetallic compound layers in friction stir welding of dissimilar Al/Mg alloys

Abstract

Frictions stir welding (FSW) and ultrasonic vibration enhanced FSW (UVeFSW) of dissimilar Al/Mg alloys were conducted, and the intermetallic compounds (IMCs) layers formed at Al/Mg interface in welds were characterised by TEM. It was found that the IMCs thickness was significantly reduced in UVeFSW, and the IMCs were generated by solid-state atomic diffusion in butt joints under the used welding conditions since the measured temperature at the tool/workpiece interface was far below the eutectic points. The EBSD characterisation showed that ultrasonic vibration improved the degree of grain recrystallization on both sides of the IMCs layers and promoted the consumption of dislocations, which resulted in a reduced diffusion rate of atoms. Therefore, the growth of IMC layer was suppressed in UVeFSW.