Ultra-rapid transient liquid phase bonding of Mg alloys within 1 s in air by ultrasonic assistance

Highlights: • AZ31B Mg alloys were successfully bonded within 1 s with the assistance of ultrasonic. • Joint was formed through liquid phase bonding and diffusion at temperatures lower than 370 °C. • Shear strengths were 31 and 42 MPa when crack propagated through MgZn₂ and MgZn eutectic, respectively. -- Abstract: An ultra-rapid transient liquid phase bonding method was successfully used to join AZ31B Mg alloys by using pure Zn interlayers in air. The bonding time was shortened to 1 s with ultrasonic assistance. Eutectic structures, MgZn, and MgZn₂ formed at relatively low temperatures of 360 °C and 370 °C. Only eutectic structures were observed at a high temperature of 380 °C because the entire joint was filled with eutectic liquid phase at this moment. MgZn₂ had higher hardness and modulus than those of MgZn. The shear strength of joint was inversely proportional to its width. The joint fractured through MgZn₂ at 360 °C and 370 °C, and through eutectoid structures at 380 °C.