Dissimilar friction stir welding of 6061 aluminum alloy and AZ31 magnesium alloy assisted with ultrasonic

Both simple interface joining and continuous intermetallic compounds (IMCs) layer formed at the interface of Al/Mg alloys during friction stir welding (FSW) deteriorates mechanical property. Based on stationary shoulder, ultrasonic was employed to assist FSW of 6061-T6 and AZ31B alloys to increase interface joining length and mixture degree of Al/Mg alloys at nugget zone (NZ). Sound joint with smooth surface is obtained, resulting from the combined effect of stationary shoulder and ultrasonic. Ultrasonic are beneficial to increasing material flow, interface joining length and mixture degree of Al/Mg alloys, improving mechanical interlocking. The tensile strength and elongation of joint with ultrasonic reach 120 MPa and 1.5%, which are higher than that without ultrasonic. Additionally, local fracture surface morphology consists of some dimples, presenting mixed fracture containing brittle and ductile fractures.