锆铜基金属玻璃隐藏液-液相变与非晶形成能力的关系研究

非晶合金在超过冷液相区加工成型可推动大块金属玻璃的广泛应用，但其发展受制于合金有限的非晶形成能力。最近研究发现，当金属玻璃加热到超过冷液相区，隐藏于快速冷却过程的液-液相变会伴随着异常放热现象显现出来，为原位研究非晶形成能力的微观机制提供了突破口。本项目拟通过原位同步辐射和中子散射等手段研究稀土元素钇的微量添加对锆铜基大块金属玻璃中隐藏液-液相变的影响机制，并探讨其与非晶形成能力之间的关系。本研究将从以下几个方面展开：1）系统研究各合金成分隐藏液-液相变过程中多尺度微观结构的演变规律；2）探讨过冷液态相变对各合金成分超过冷液体结晶行为的影响机制；3）研究隐藏液-液相变的热力学本质，获得锆铜基合金超过冷液相区亚稳相图，并总结其与非晶形成能力之间的关系。本研究将为微合金化调控金属玻璃超过冷液体液-液相变行为提供实验依据，同时为具有良好性能的大块金属玻璃的研发及其加工成型工艺的设计提供重要参考。

The processing of metallic glasses (MGs) in the supercooled liquid region provides a unique way for their wide applications but is hindered by the limited glass-forming ability (GFA) of alloys. Liquid-liquid phase transition (LLPT) opens a window to investigate the multi-scale structure evolution of glass formation. However, the LLPT is easy to be suppressed during the quenching process of metallic-glass forming melts. Most recently, a hidden liquid-liquid phase transition (HLPT) can be brought out with an anomalous exothermic peak when heating the MGs to their supercooled liquid regions. Therefore the HLPT provides a unique opportunity to in-situ study the microstructure origin of GFA. We will study the effects of micro-alloying of Re elements such as Y on the HLPT in ZrCu-based MGs using a suite of in-situ techniques, including synchrotron and neutron scattering, and further, reveal its correlation with GFA. There are several aspects of this project. First, we will obtain the direct multi-scale structure evidence of the occurrence of the HLPT for the ZrCu-based alloys with the Y addition. Second, we will reveal the structure origin by in-situ study the effect of the HLPT on crystallization pathways for the studied alloy system. Third, we will investigate the thermodynamic nature of the HLPT and provide a metastable phase diagram by summarizing the principle of the phase transition for the ZrCu-alloys. Finally, the relationship between the HLPT with the GFA will be revealed. Our project will provide the theoretical and experimental basis for tuning the behavior of the LLPT by micro-alloying, which would shed light on developing novel BMGs with tunable properties and promoting their processability.