Spieckermann Florian, Şopu Daniel, Soprunyuk Viktor, Kerber Michael B, Bednarčík Jozef, Schökel Alexander, Rezvan Amir, Ketov Sergey, Sarac Baran, Schafler Erhard, Eckert Jürgen
Department of Materials Science, Chair of Materials Physics, Montanuniversität Leoben, Jahnstraße 12, 8700, Leoben, Austria.
Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences, Jahnstraße 12, 8700, Leoben, Austria.
Nat Commun. 2022 Jan 10;13(1):127. doi: 10.1038/s41467-021-27661-2.
The atomistic mechanisms occurring during the processes of aging and rejuvenation in glassy materials involve very small structural rearrangements that are extremely difficult to capture experimentally. Here we use in-situ X-ray diffraction to investigate the structural rearrangements during annealing from 77 K up to the crystallization temperature in CuZrAlHfCo bulk metallic glass rejuvenated by high pressure torsion performed at cryogenic temperatures and at room temperature. Using a measure of the configurational entropy calculated from the X-ray pair correlation function, the structural footprint of the deformation-induced rejuvenation in bulk metallic glass is revealed. With synchrotron radiation, temperature and time resolutions comparable to calorimetric experiments are possible. This opens hitherto unavailable experimental possibilities allowing to unambiguously correlate changes in atomic configuration and structure to calorimetrically observed signals and can attribute those to changes of the dynamic and vibrational relaxations (α-, β- and γ-transition) in glassy materials. The results suggest that the structural footprint of the β-transition is related to entropic relaxation with characteristics of a first-order transition. Dynamic mechanical analysis data shows that in the range of the β-transition, non-reversible structural rearrangements are preferentially activated. The low-temperature γ-transition is mostly triggering reversible deformations and shows a change of slope in the entropic footprint suggesting second-order characteristics.
玻璃态材料老化和恢复过程中发生的原子机制涉及非常小的结构重排，极难通过实验捕捉。在此，我们使用原位X射线衍射研究经低温和室温下高压扭转恢复的CuZrAlHfCo块体金属玻璃从77 K退火至结晶温度过程中的结构重排。通过测量由X射线对相关函数计算出的组态熵，揭示了块体金属玻璃中变形诱导恢复的结构特征。利用同步辐射，可实现与量热实验相当的温度和时间分辨率。这开启了迄今无法获得的实验可能性，能够明确地将原子构型和结构的变化与量热观测信号相关联，并将这些归因于玻璃态材料中动态和振动弛豫（α-、β-和γ-转变）的变化。结果表明，β-转变的结构特征与具有一级转变特征的熵弛豫有关。动态力学分析数据表明，在β-转变范围内，不可逆的结构重排优先被激活。低温γ-转变主要引发可逆变形，并在熵特征中显示出斜率变化，表明具有二级特征。
