Microstructure and formation mechanism of Al2O3/Zn5Al/2024Al joint by ultrasonic assisted soldering process

Abstract

Zn5Al filler metal was used to join 2024Al and Al2O3 ceramic with the ultrasonic assisted soldering process in the atmospheric environment. Al2O3 ceramics were dipped by molten Zn5Al alloy (melting temperature: 382 °C) with the time of ultrasonic action for 5– 600 s, respectively. During the ultrasonic assisted soldering process, the ultrasonic was applied for 1 s, the Al2O3 ceramic was subjected to a pressure of 0.2 MPa. To reduce the residual stress, the soldered joint was cooled in the furnace. 2024Al had better metallurgical fusion with Zn5Al filler metal. The grain boundary on the 2024Al was partially dissolved by Zn5Al filler metal. The fan-shaped α-Al eutectic phases were distributed on the gradient layer. With the increase of the ultrasonic dipping time, more fine β-ZnAl phases were accumulated on the Al2O3 ceramic surface. The Al2O3/Zn5Al/2024Al joint with ultrasonic dipping time of 600 s had the highest shear strength (39.53 MPa). The soldered joint fractured mainly in cohesive failure mode, and the joint broke from the Zn5Al filler metal.