Overwhelming oxide films fragmentation and interfacial reaction mechanisms in ultrasonic-assisted brazing of Al-foam/Cu using semi-molten Zn–14Al filler

This study investigates interfacial interactions in perforated aluminum foam/Zn-14Al/Cu joints formed via ultrasonic-assisted brazing, with a novel focus on cavitation-driven oxide film fracture at 420°C. Ultrasonic-induced cavitation in semi-molten filler generates localized energy that breaks Cu oxide films into micron-scale fragments, a key mechanism enabling effective joint formation. Critical findings show that increased ultrasonic amplitude accelerates filler wetting and modifies the composition and hardness of intermetallic compounds (CuZn 5 , Al 3 Cu 5 Zn 2 , Al 4.2 Cu 3.2 Zn 0.7 ) in the brazed seam. The joints achieved an average shear strength of 3.61 MPa, highlighting the pivotal role of ultrasonic amplitude in optimizing performance. This work advances understanding of cavitation-mediated metallurgical processes in ultrasonic brazing, offering valuable insights for enhancing joint quality in similar material systems.