Probing the atomic structure and physical properties of super-cooled liquid alloys during vitrification

这项工作的范围是揭示液态金属的结构如何在其途径中发生变化。当熔化的合金足够快地冷却以避免在凝固时结晶时，形成金属玻璃。然而，液体的原子结构转化为玻璃态结构的方式通常是未知的，主要是因为在过冷液体状态下结构信息的获取受到结晶的阻碍。在这项工作中，我们能够克服这一限制，并实现原位玻璃化的各种金属合金在高能量同步辐射束，使用最先进的空气动力悬浮技术的状态。这一重要成就使得能够获得从液体到过冷液体和玻璃态的整个范围内的结构数据，为研究玻璃化过程中的结构演变提供了独特的可能性。结果表明，存在三个非结晶制度的液体的途径玻璃化。低于熔化温度的结构演变偏离液体的结构演变，指向液体结构演变中的交叉。在短期和中期范围内（SRO和MRO）的本地秩序迅速增加，作为过冷液体接近玻璃化转变温度Tg，低于该结构“冻结”。发现过冷液体中的结构重排与金属液体在冷却时粘度的快速增加相关。

The scope of this work is to uncover how the structure of liquid metals changes in their pathway to vitirification. A metallic glass is formed when a melted alloy is cooled rapidly enough so that crystallization is avoided upon solidification. However, the way the atomic structure of the liquid converts to the glassy structure is generally unknown, mainly because the acquisition of structural information in the supercooled liquid regime is hindered by crystallization. In this work we were able to overcome this limitation and achieve in-situ vitrification of various metallic alloys in a high energy synchrotron beam using a state of the art aerodynamic levitation technique. This important achievement allowed the acquisition of structural data in the whole range from the liquid through the super-cooled liquid and the glassy state offering a unique possibility to study the structural evolution during vitrification. The results indicate the existence of three non-crystalline regimes in the liquid’s pathway to vitrification. The structural evolution below the melting temperature deviates from that of the liquid, pointing to a crossover in the evolution of the liquid’s structure. The local order in the short and medium range (SRO and MRO) increases rapidly as the supercooled liquid approaches the glass transition temperature Tg, below which the structure “freezes”. The structural rearrangements in the supercooled liquid are found to be correlated with a rapid increase in viscosity of metallic liquid upon cooling.