Forming of metallic glasses: mechanisms and processes

Abstract Metallic glasses (MGs) with amorphous structures and tunable compositions have been considered excellent structural and functional materials, especially in the frontier fields of microelectromechanical systems (MEMS), biomedical engineering, energy conversion, etc. Making these materials into desired structures for different applications has always been one of the research focuses in the past decades. Due to high strength and poor plasticity at ambient temperature, MGs are difficult to be formed and manufactured by conventional approaches. Thermoplastic forming, utilizing the superplasticity property of MGs in supercooled liquid region, has been developed to fabricate micro-/nanofeatures. However, the thermal effect inevitably increases the risks of crystallization and oxidation of MGs during forming, leading to material performance degradation and limiting the process feasibility to specific composition systems of MGs. In view of this, a novel strategy proposed recently is to promote plastic deformation and forming of MGs by high frequency ultrasonic vibration at room temperature, which promises to avoid the shortcomings in thermal forming and extend the forming processes of MGs. In this review article, we would like to first discuss the forming mechanisms of supercooled MGs liquid, the joining of MGs and a variety of fabricated structures based on thermoplastic forming. After that, a concept of ultrasonic-assisted forming of MGs is introduced focusing on plastic behavior under high frequency vibration and the latest process advances including shear punching and manufacturing. Finally, the existing problems and the development prospects will be discussed to facilitate the further researches on MGs forming.