Effect of SiC Particles Content on Microstructure and Shear Strength of the Al₂O₃/Zn5Al−xSiC/2024Al Joint

Zn5Al−xSiC composite solder was used to join Al₂O₃ ceramic and 2024Al with ultrasonic‐assisted soldering process. Before the soldering of Al₂O₃ ceramic and 2024Al, the Al₂O₃ ceramics were wetted by molten Zn5Al solder under the action of ultrasonic. In the process of ultrasonic wetting, Al element in Zn5Al solder and O element are formed Al₂O₃ on the Al₂O₃ ceramic surface. SiC particles are mixed with molten metal at 420 °C by mechanical agitation. SiC particles effectively prevent solder from shrinking during cooling. In the soldered seam, Zn element diffuses to 2024Al base metal along the grain boundary and dissolves the Al grains in 2024Al to form a diffusion layer in the soldered seam. At the same time, SiC particles refine the microstructure grain in the soldered seam and strengthens the mechanical properties of the solder. The Al₂O₃/Zn5Al‐7 wt% SiC/2024Al joint strength is up to 66 Mpa, which was increased by 70% compared with Al₂O₃/Zn5Al/2024Al joint (39 MPa). However, the strength of the Al₂O₃/Zn5Al‐9 wt% SiC/2024Al joint drops sharply to 23 MPa. Excessive SiC particles formed agglomerates inside the solder and reduced the fluidity of the solder.