Abstract The change of physical properties during aging and the associated microscopic dynamics of the Au49Cu26.9Si16.3Ag5.5Pd2.3 bulk metallic glass are investigated using a broad collection of laboratory and synchrotron-based techniques, such as differential- and fast-scanning calorimetry, thermomechanical testing, and x-ray photon correlation spectroscopy. We observe multiple decays in the enthalpy change during aging. This is reflected by a microscopic ordering consisting of distinct stationary dynamical regimes interconnected by abrupt aging processes. The stationary regimes are representative of states of local and transient equilibrium with increasingly higher activation energies. Furthermore, the aging study is conducted with the kinetically fragile frozen-in structure and the underlying fragile-to-strong transition is accessed by the ultra-viscous liquid state during annealing on a long-time scale and corresponds to the last observed enthalpy equilibration decay. The experimental work verifies, for the first time, that in a metallic glass forming system, the fragile-to-strong transition can also occur below the conventional glass transition temperature. Upon reheating, the reverse transformation, i.e. the strong-to-fragile transition, is observed with an entropy change of 0.19 J/(g-atom K), which is 2.4% of the entropy of fusion.

中文翻译：

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金属玻璃成型体退火后的分级老化途径和可逆的脆到强转变

摘要 使用大量实验室和基于同步加速器的技术（如差示扫描量热法和快速扫描量热法）研究了老化过程中物理性质的变化以及 Au49Cu26.9Si16.3Ag5.5Pd2.3 块状金属玻璃的相关微观动力学、热机械测试和 X 射线光子相关光谱。我们观察到老化过程中焓变的多次衰减。这通过由突然老化过程相互连接的不同静态动态机制组成的微观排序反映出来。静止状态代表具有越来越高的活化能的局部和瞬态平衡状态。此外，老化研究是用动力学脆弱的冻结结构进行的，潜在的脆弱到强转变是在长期退火过程中通过超粘性液态获得的，并且对应于最后观察到的焓平衡衰减。实验工作首次证实，在金属玻璃成型系统中，从脆到强的转变也可以在低于常规玻璃转变温度的情况下发生。在重新加热时，观察到逆转变，即从强到脆的转变，熵变化为 0.19 J/(g-atom K)，这是聚变熵的 2.4%。在金属玻璃成型系统中，从脆到强的转变也可能在低于常规玻璃化转变温度的情况下发生。在重新加热时，观察到逆向转变，即从强到脆的转变，熵变化为 0.19 J/(g-atom K)，这是聚变熵的 2.4%。在金属玻璃成型系统中，从脆到强的转变也可能在低于常规玻璃化转变温度的情况下发生。在重新加热时，观察到逆转变，即从强到脆的转变，熵变化为 0.19 J/(g-atom K)，这是聚变熵的 2.4%。