Recently, the Institute of Mechanics of the Chinese Academy of Sciences has cooperated with researchers at home and abroad to make new progress in the anti-aging of glass materials, and for the first time experimentally realized the extremely youthful structure of a typical metallic glass in an ultra-fast time scale. The related results are titled Ultrafast extreme rejuvenation of metallic glasses by shock compression, published in Science Advances (Science Advances 5: eaaw6249 (2019)).
The metastable glass material has a tendency of spontaneous aging to the thermodynamic equilibrium state, and at the same time, it is accompanied by deterioration of material properties. However, through the input of external energy, the aging glass material can rejuvenate the structure (rejuvenation). This anti-aging process on the one hand contributes to the basic understanding of the complex dynamic behavior of glass, on the other hand it is also conducive to the engineering application of glass materials. In recent years, for metallic glass materials with broad application prospects, a series of structural rejuvenation methods based on non-affine deformation have been proposed in order to effectively control the mechanical and physical properties of the materials. However, all previous rejuvenation methods work at lower stress levels and require a sufficiently long time scale, and therefore have great limitations.
Researchers based on the dual-target plate impact technology of the light gas gun device, realized that the typical zirconium-based metallic glass quickly rejuvenated to a high level in about 365 nanoseconds (one millionth of the time it takes for a person to blink an eye). Enthalpy is extremely disordered. The challenge of this technology is to apply several GPa-level single-pulse loading and transient automatic unloading to metallic glass, so as to avoid dynamic failure of materials such as shear bands and spallation; at the same time, by controlling the impact speed of the flyer, the metal The rapid rejuvenation of glass “freezes” at different levels.
Researchers have conducted a comprehensive study on the ultra-fast rejuvenation process of metallic glass from the perspectives of thermodynamics, multi-scale structure and phonon dynamics “Bose peak”, revealing that the rejuvenation of glass structure comes from nano-scale clusters. Free volume induced by the “shear transition” mode. Based on this physical mechanism, a dimensionless Deborah number is defined, which explains the possibility of the time scale of ultra-fast rejuvenation of metallic glass. This work has increased the time scale for the rejuvenation of metallic glass structures by at least 10 orders of magnitude, expanded the application fields of this type of material, and deepened people’s understanding of the ultrafast dynamics of glass.
Post time: Dec-06-2021