The roles of ultrasonic techniques for metallic glasses: processing, microstructure and applications

Metallic glasses (MGs), although regarded as promising structural materials due to their superior properties such as high elastic limit, strength, and superior corrosive resistance, face two pressing issues: their low glass forming ability (GFA) and poor macroscopic plasticity at room temperature. Many studies have been devoted to decoding the inherent factors of the limited GFA and brittleness from microstructures, deformation mechanisms, and processing routes. For enhancing the GFA, approaches regarding design strategies such as machining learning (ML), high-throughput screening (HTS), and processing techniques such as ultrasonic vibration (UV) loading and 3D printing have been proposed till now. The strategies of ML and HTS tend to explore new compositions of glass formers with higher GFA. By contrast, the UV loading aims to combine the existing glassy alloys with different or the same compositions into a larger one. For improving the tensile plasticity and work-hardening, a few strategies such as tuning the microstructures (designing and fabricating the glassy composites and developing the glassy-crystalline laminated alloys as well as the rejuvenation of glassy alloys, etc.) have been proposed. A few studies indicated that the UV loading not only enhances the GFA but also improves plasticity by optimizing the microstructures via rejuvenation. These merits make UV loading a very promising strategy for improving glassy alloys. This review summarizes the recent advances of UV loading and provides a comprehensive understanding of the technique in terms of principles, influence factors, and processing parameters.