Interfacial Structure and Formation Mechanism of Ultrasonic-assisted Brazed Joint of SiC Ceramics with Al[sbnd]12Si Filler Metals in Air

Ultrasonic-assisted brazing of SiC ceramics was performed by filling with an Al[sbnd]12Si alloy at a low temperature of 620 °C in air. The interfacial characteristics and formation mechanism were investigated. The joint shear strength reached 84–94 MPa using the ultrasonic time of 2–16 s. The fracture morphology showed that the fracture path initiated and propagated in the joint alloy. The thin film of amorphous SiO₂ that formed on the SiC surface was non-uniformly decomposed and diffused into the liquid Al[sbnd]12Si alloy under the cavitation erosion effect of ultrasound. Abnormal isolated blocks of Al₂SiO₅ compounds formed at the interface between Al[sbnd]12Si and a thicker SiO₂ layer formed during the thermal oxidation treatment of the SiC ceramic. The SiO₂ layer on the SiC ceramic did not hinder or impair the wetting and bonding process, and a stronger bond could form between Al[sbnd]12Si and SiO₂ or SiC in ultrasonic-assisted brazing.