金属玻璃异常Sub-Tg弛豫行为及其与液体动力学性质的相关性研究

The relaxation behavior of metallic glasses is a frontier problem, as well as a hot issue, in condensed matter physics and material science. The study of the correlation between the abnormal sub-Tg relaxation in metallic glasses (MGs) and kinetic properties of corresponding alloy liquids is of great importance not only for better understanding the nature of glass transition, improving the stability of MGs, uncovering the microstructural inheritance during the liquid-solid transformation, but also for promoting the standardization during the production and treatment technology of MGs. In this project, we start with the characteristic of abnormal sub-Tg relaxation patterns in different hyperquenched MG ribbons. Then, we focus on investigating how these characteristic of the sub-Tg relaxation anomaly in glassy solids is linked to abnormal kinetic properties in the corresponding alloy liquids, i.e., the fragile-to-strong transition and the liquid-liquid phase transition. On the bridge of clusters, we attempt to reveal the dominant structure units determining this link and further uncover the evolution of these structure units during cooling. The nature of the microstructures that determines the abnormal sub-Tg relaxation during cooling from the superheated liquid to supercooled liquid to glass transition could be discovered. By introducing an additional factor representing the kinetic properties of alloy liquids to the improved thermodynamic model that predicts the monotonic enthalpy evolution of metallic glasses, a perfect model that could quantitatively predict the abnormal relaxation behaviors in hyperquenched MGs, as well as the non-monotonic enthalpy relaxation manner, will be obtained.

金属玻璃弛豫是凝聚态物理和材料科学研究领域的前沿和热点问题。研究金属玻璃异常Sub-Tg弛豫与液体动力学性质的相关性对于深入理解玻璃转变理论、探讨液固遗传微观结构本质、提高金属玻璃稳定性、促进金属玻璃制备和处理工艺标准化等问题均具有极其重要的意义。本课题以研究超快速冷却条件下金属玻璃带材异常Sub-Tg弛豫特征为起点，着重探讨金属玻璃异常Sub-Tg弛豫行为与对应合金液体的强脆转变、液液相变等动力学特殊现象宏观特征的密切联系，并以团簇为桥梁，揭示决定该密切联系的特征结构单元及其演变规律，确定高温液体-过冷液体-玻璃转变过程中决定异常Sub-Tg弛豫行为的液固遗传微观结构本质，通过在改良的热焓弛豫模型中进一步引入表征液体动力学性质的附加因子，构建超快速凝固条件下金属玻璃固体异常Sub-Tg弛豫行为及非单调焓变的定量预测模型。

金属玻璃弛豫是凝聚态物理和材料科学研究领域的前沿和热点问题。研究金属玻璃异常Sub-Tg弛豫与液体动力学性质的相关性对于深入理解玻璃转变理论、探讨液固遗传微观结构本质、提高金属玻璃稳定性、促进金属玻璃制备和处理工艺标准化等问题均具有极其重要的意义。本课题以研究超快速冷却条件下金属玻璃带材异常Sub-Tg弛豫和异常晶化演变规律为起点，着重探讨金属玻璃异常Sub-Tg弛豫行为、高温熔体的液液相变、过冷液体的强脆转变等宏观特征的相互联系，并以团簇为桥梁，揭示决定该密切联系的特征结构单元及其演变规律，确定高温液体-过冷液体-玻璃转变过程中决定异常Sub-Tg弛豫行为的液固遗传微观结构本质。已经发现，beta弛豫参与金属玻璃条带Sub-Tg弛豫的起始温度与冷却速度、液体的脆性密切相关；在没有异常Sub-Tg弛豫现象的合金体系中，普遍存在晶化的异常演变行为，该行为和非晶固体的异常弛豫行为均为过冷液体中强脆转变行为的表现；大块金属玻璃体系中，高温熔体的液液相变强度和过冷液体中的强脆转变程度具有明显的负相关关系；大块金属玻璃和边缘合金体系的液液相变行为具有不同的结构演变图景；对于大块金属玻璃体系，其液液相变行为由具有较大脆性的二十面体团簇随温度的演化规律决定，该特征结构信息的演变同样可以描述强脆转变和液液相变的负相关关系；不同金属玻璃液体的弛豫时间（及动力学不均匀性）随温度变化具有普适定量描述，金属玻璃液体的弛豫行为与动力学不均匀性存在普遍关联；通过在改良的热焓弛豫模型中进一步引入表征液体动力学性质的附加因子，初步实现了超快速凝固条件下铜锆金属玻璃条带非单调焓变的半定量预测模型。