Microstructure, mechanical properties and mechanism of ultrasound-assisted rapid transient liquid phase bonding of magnesium alloy in air

An ultrasound-assisted transient liquid phase (U-TLP) bonding process for magnesium alloy has been developed to shorten the bonding time and operate in air. The optimized joint shear strength can reach 109.3 MPa, which is 100% of base metal. The mechanism of this rapid U-TLP process has been investigated based on the microstructure evolution, phase composition, mechanical properties, and fracture path. The results indicate that the surface oxide films were successfully removed by ultrasonic. The intermetallic compounds (IMCs) in the joint were decreased by increasing bonding temperature. A full solid solution joint interface without IMCs or pores was obtained by applying a two-step U-TLP process: first ultrasonic at 370 degrees C and second ultrasonic at 490 degrees C. The time needed for isothermal solidification process was significantly shortened to several seconds, due to liquid squeezing out and accelerated diffusion. (C) 2015 Elsevier Ltd. All rights reserved.