Joint formation and mechanical properties of ultrasonic-assisted transient liquid bonding of dissimilar Al/Mg with a Zn interlayer in air

Abstract

In this work, ultrasonic-assisted transient liquid bonding (UATLP) was used to rapidly join dissimilar Al/Mg alloys in the air. The pure Zn interlayer was chosen to prevent Al–Mg intermetallic compounds (IMCs). The effects of the bonding time on the microstructure and mechanical properties of the joints were studied. The joint formation mechanism was analyzed. Results show that the Al–Mg IMCs can be avoided when the ultrasonic time was shorter than 3 s. The oxide layer on the Al substrate was incompletely removed when the ultrasonic time was shorter than 2 s, and the joint was characterized by Mg–Zn eutectic, MgZn, and MgZn2 from the Mg side to the Al side. The joint had a shear strength of 16 MPa and failed through the MgZn2/Al interface under such condition. The oxide layer on the Al substrate was removed when the ultrasonic time was increased to 3 s. The joint had a shear strength of 24 MPa, and it failed through the MgZn2 layer and the Mg–Zn eutectic. The entire Zn foil interacted with the Mg and Al substrate at a prolonged ultrasonic time of 6 s. Al–Mg IMCs of Al3Mg2 and Al12Mg17 appeared because a large amount of Al and Mg atoms diffused into the joint. The joint strength decreased to 11 MPa and failed through the Al3Mg2 layer.