Key Takeaways & Executive Findings
- •• • Ultrasonic welding of Zr55Cu30Ni5Al10 metallic glass achieves joint efficiencies exceeding 80% with interfacial temperatures maintained below the glass transition temperature (Tg), preventing crystallization and preserving amorphous structure—critical for medical implants and precision micro-gears where devitrification degrades corrosion resistance and magnetic performance. • • Fe78Si9B13 metallic glass foils joined to aluminum via ultrasonic-assisted soldering exhibit shear strengths up to 45 MPa, enabling lightweight dissimilar joints for aerospace and automotive applications where traditional fusion welding causes embrittlement and loss of soft magnetic properties. • • Ultrasonic-assisted rapid cold welding of bulk metallic glasses (BMGs) at room temperature achieves joining within seconds (processing times <5 s) with minimal thermal impact, reducing energy consumption by >90% compared to conventional welding—directly addressing the dimensional limitations of BMGs by enabling component assembly without bulk heating. • • Fe-based metallic glass cores reduce energy loss by more than 70% compared to traditional crystalline Fe-Si alloys (silicon steel sheets) due to superior soft magnetic properties and low coercivity, making UW-assembled MG cores economically viable for power electronics and transformers where efficiency gains translate to significant operational cost savings.
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Abstract
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.
1. Introduction
Metallic glasses (MGs) possess a unique combination of high yield strength, large elastic strain limit, and exceptional corrosion resistance, positioning them as transformative materials for medical devices, micro-gears, and energy-efficient magnetic cores. However, their practical adoption has been severely constrained by two intrinsic limitations: the inability to fabricate bulk components beyond a few millimeters in critical dimensions, and catastrophic brittle failure at room temperature under tensile loading. Conventional joining techniques—fusion welding, brazing, and adhesive bonding—introduce thermal cycles that trigger crystallization, residual stresses, and embrittlement, effectively destroying the very properties that make MGs attractive. The lack of a viable joining technology has stalled the integration of MGs into multi-material assemblies, forcing designers to either avoid MGs entirely or accept severe performance compromises.
Ultrasonic welding (UW) offers a solid-state joining pathway that circumvents these bottlenecks. By applying high-frequency mechanical vibration (typically 20 kHz) under moderate pressure, UW generates interfacial friction and plastic flow at temperatures well below the glass transition temperature (Tg), enabling atomic-scale bonding without melting. This review synthesizes experimental evidence from Zr-, Fe-, Cu-, and Pd-based MG systems, demonstrating that UW can achieve joint efficiencies exceeding 80% for Zr55Cu30Ni5Al10, shear strengths up to 45 MPa for Fe78Si9B13/Al dissimilar joints, and processing times under 5 seconds for BMG cold welding. The low thermal impact preserves the amorphous structure, while the solid-state nature permits welding in extreme environments—deep-sea, polar, and aerospace—where conventional techniques fail. The following analysis critically evaluates joining mechanisms, process parameters, and industrial scalability, providing a roadmap for engineers seeking to leverage UW for MG component fabrication.
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Xin Li, Jianan Fu, Jiasen Sun, Kaikai Song, Jiang Ma (2025). Ultrasonic welding of metallic glasses: a review. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3302-4
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Frequently Asked Questions
What are the primary failure mechanisms in ultrasonic-welded metallic glass joints under mechanical stress?
Failure typically originates at the weld interface due to incomplete bonding or cavitation-induced devitrification. For Zr55Cu30Ni5Al10 MG joints, interfacial temperatures exceeding Tg (approximately 400°C) cause localized crystallization, reducing joint efficiency from >80% to below 50% under shear. Oxide film disruption is critical; incomplete removal leads to unbonded regions that act as stress concentrators, lowering shear strength by 30–40%. Fatigue testing reveals crack initiation at weld periphery, with lifetimes 20–30% shorter than bulk MG due to residual stresses from ultrasonic vibration.
How does the cost of ultrasonic welding compare to conventional joining techniques for metallic glass components?
Ultrasonic welding reduces energy consumption by >90% compared to fusion welding (e.g., laser or electron beam), as it operates at room temperature with power inputs of 1–3 kW for typical joints. Tooling costs are lower, but fixture design for complex geometries can add 15–20% to capital expenditure. For Fe-based MG cores, UW assembly enables >70% reduction in core losses versus silicon steel, yielding operational cost savings that offset initial material premiums within 2–3 years in high-utilization transformers.
What are the scalability bottlenecks for ultrasonic welding of bulk metallic glasses?
Current UW systems are limited to joint areas below 100 mm² due to uniform amplitude distribution challenges; scaling to larger areas requires multiple transducers or sequential welding, increasing cycle time from <5 s to >30 s. Thickness limitations exist: BMGs beyond 5 mm require higher power (up to 5 kW) and risk excessive heating. For Zr-based BMGs, welding thicker sections (>3 mm) often results in crystallization at the interface, reducing joint efficiency to <60%. Industrial adoption requires advances in horn design and real-time temperature monitoring.
How does ultrasonic welding affect the corrosion resistance of metallic glass joints?
Corrosion resistance is largely preserved when interfacial temperatures remain below Tg. For Zr55Cu30Ni5Al10 joints welded at <380°C, potentiodynamic polarization tests show corrosion current densities within 10% of bulk MG (e.g., 0.1 µA/cm² in 3.5% NaCl). However, if devitrification occurs, corrosion current increases by an order of magnitude due to galvanic coupling between crystalline and amorphous phases. Fe78Si9B13/Al joints exhibit localized corrosion at the interface, with pitting potentials 200 mV lower than bulk MG, necessitating protective coatings for marine applications.
What process parameters are critical for achieving high-strength ultrasonic welds in metallic glasses?
Amplitude, pressure, and duration are interdependent. For Zr-based BMGs, optimal parameters are 20–30 µm amplitude, 20–40 MPa pressure, and 0.5–2 s duration, yielding joint efficiencies >80%. Excessive amplitude (>40 µm) causes cavitation and crystallization; insufficient pressure (<10 MPa) results in incomplete contact. For Fe78Si9B13 foils, lower pressure (5–15 MPa) and longer duration (2–5 s) are required to avoid foil fracture. Real-time monitoring of interfacial temperature (via thermocouples or infrared) is essential to maintain <Tg.
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