Microstructure and Formation Mechanism of Ultrasound-Assisted Transient Liquid Phase Bonded Magnesium Alloys with Ni Interlayer

Abstract

Ultrasound-assisted transient liquid phase bonding (U-TLP) has been regarded as a promising brazing process to join magnesium alloys with a Sn and Zn interlayer; however, the formation of brittle magnesium intermetallic compounds (Mg2Sn, MgZn, and MgZn2) compromises the mechanical properties of the joints. In this study, Mg alloy U-TLP joints with a Ni interlayer were evaluated based on shear strength and hardness measurement. Microstructural evolution along with ultrasonic duration time and intermetallic compound formation were characterized using X-ray diffraction and electron microscopy methods. The results show that incremental ultrasonic durations of up to 30 s lead to the microstructural evolution from the Mg2Ni layer, eutectic compounds (Mg2Ni and α-Mg) to α-Mg (Ni), accompanied by shear strength increases. The maximum value of the shear strength is 107 MPa. The role that ultrasound vibration played in brazing was evaluated, and showed that the MgO film was broken by the acoustic softening effect when the interlayer and base metal were solid. As the MgO and Mg substrate have different stress reduction τ, this plastic mismatch helps to break the oxide film. Additionally, the diffusion between the solid Mg substrate and Ni interlayer is accelerated greatly by the acoustic pressure based on the DICTRA dynamic calculation.

Effect of MBF-20 Interlayer on the Microstructure and Corrosion Behaviour of Inconel 625 Super Alloy after Diffusion Brazing

“…In this circuit, R s is the resistance of the electrolyte, C ox is the capacitance of the oxide layer, R ox is the resistance of the oxide layer, R ct is the charge transfer resistance, and C dl is the capacitance of the double layer. A CPE element was used, whose impedance was calculated based on Equation (10), because the double layer formed on the electrode surface acts as a non-ideal capacitor, instead of using C as the ideal capacitor capacity.…”

“…A study on the diffusion brazing of an Ni-based superalloy with a B-rich interlayer reported that the microstructure of the joint after partial isothermal solidification consists of three main sub-regions [ 7 , 8 , 9 , 10 , 11 ] as follow:…”

Microstructure and Properties of Magnesium Alloy Joints Bonded by Using Gallium with the Assistance of Ultrasound at Room Temperature

“…The joints consisted of AgMg 3 , CuMg 2 , and α-Mg solid solution, and the fracture morphology was characterized by brittle fractures when considering short durations, but presented ductile characteristics with longer exposure to ultrasound. Li et al chose Ni as an interlayer for bonding Mg-Mn-Ce alloy at 520 • C to explore the effect of ultrasonic vibration time on the microstructure and mechanical properties of joints [11]. With incremental increases in time up to 30 s, the shear strength increased from 19 MPa to 92 MPa, which might have resulted from a decrease in the amount of IMCs.…”

Ultrasonically enhanced flux-less bonding with Zn-5Al alloy under ambient condition for high-temperature electronics interconnects

“…It is recognised that TLPS process can be accelerated by ultrasonic vibration. Ultrasound-assisted transient liquid phase soldering (U-TLPS) has been employed as a promising brazing process [24][25]; it has been applied by several researchers for ultrasonic-assisted soldering process with Zn-based alloys [20][21][22], but none has attempted to apply ultrasonic vibration for TLPS process, which can also be beneficial.…”