Hierarchical aging pathways and reversible fragile-to-strong transition upon annealing of a metallic glass former
Hierarchical aging pathways and reversible fragile-to-strong transition upon annealing of a metallic glass former
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DOI：
10.1016/j.actamat.2017.10.060
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发表时间：
2018-02-01
期刊：
影响因子：
9.4
通讯作者：
Ruta, Beatrice
中科院分区：
文献类型：
--
作者：
Gallino, Isabella;Cangialosi, Daniele;Ruta, Beatrice
老化过程中的物理性能的变化和相关的微观动力学的Au49Cu26.9Si16.3Ag5.5Pd2.3大块金属玻璃的研究使用广泛的收集实验室和同步加速器为基础的技术，如差示和快速扫描量热法，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。这是反映了由不同的静态动态系统互连的突然老化过程组成的微观有序。稳定的制度是代表的本地和瞬态平衡的状态越来越高的活化能。此外，老化研究进行了动力学脆弱的冻结结构和基础的脆弱到强大的转变是由超粘液体状态在退火过程中的长时间尺度上访问，并对应于最后观察到的焓平衡衰减。实验工作首次证实了在金属玻璃形成系统中，在低于常规玻璃转变温度下也可以发生脆强转变。在再加热时，观察到相反的转变，即强到脆的转变，熵变为0.19 J/（g-原子K），这是熔合熵的2.4%。(C)2017 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
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. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.