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 (CuZn₅, Al₃Cu₅Zn₂, Al_4.2Cu_3.2Zn_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.