Ultrasonic welding of metallic glasses: a review
Metallic glasses (MGs) exhibit high strength, high elasticity, and excellent corrosion resistance, yet their practical deployment is constrained by limited dimensions and room-temperature brittleness. Ultrasonic welding (UW), a solid-state joining technique, has emerged as a viable route to overcome these limitations. This review critically examines the role of UW in enhancing MG manufacturability, emphasizing low thermal impact, rapid processing, and suitability for extreme environments including deep-sea, polar, and aerospace settings. The paper synthesizes joining mechanisms specific to MGs, drawing on experimental evidence from Zr-, Fe-, Cu-, and Pd-based systems. Key findings include: UW of Zr55Cu30Ni5Al10 MG achieves joint efficiencies exceeding 80% with interfacial temperatures below the glass transition temperature (Tg); Fe78Si9B13 MG foils can be joined to aluminum with shear strengths up to 45 MPa; and ultrasonic-assisted cold welding of bulk metallic glasses (BMGs) enables rapid joining at room temperature with minimal crystallization. The review also highlights challenges such as cavitation-induced devitrification, oxide film disruption, and scalability for large components. Industrial implications span medical device assembly, micro-gear fabrication, and energy-efficient magnetic cores, where Fe-based MGs reduce core losses by >70% compared to silicon steel. The analysis underscores UW as a low-cost, energy-efficient pathway for integrating MGs into high-value engineering systems, while identifying critical parameters—amplitude, pressure, and duration—that govern joint integrity and microstructural stability.