二元非晶合金晶化热力学与动力学研究

There is a typical technique for preparing nano-crystalline materials, i.e., crystallization of amorphous alloys, which holds an important position in engineering practice. Since the crystallization involves the change of structure and properties, the theoretical work on crystallization has been paid extensive attention. In the previous treatment, it was generally considered that driving force describes system state, and energy barrier describes crystallization process, but the relationship between them was neglected. However, it has been realized from many experimental evidences that an intrinsic relationship between the driving force and energy barrier may exist. On this basis, two binary amorphous alloys with different thermal stabilities, i.e., Fe-B system and Cu-Zr system, will be chosen as the objects of study in this project. The atomic-level structure and crystallization behavior of the two amorphous alloys will be studied. First, the atomic-level structure of amorphous alloys will be quantitatively characterized based on experimental research. Then, the vital physical link between structure and crystallization behavior will be clarified, and the functional relation representing the relationship between driving force and energy barrier will be specifically obtained. Finally, the correlations among driving force, energy barrier, thermodynamic and kinetic properties will be revealed, and the relationship between thermodynamic and kinetic properties of amorphous alloys will be investigated from the viewpoint of crystallization. This project will promote the development of theoretical model on crystallization, and provide a theoretical basis for the understanding of amorphous materials.

非晶晶化法作为制备纳米晶体材料的典型方法在工程领域中占据重要地位。晶化过程涉及结构、性质等的变化，因此关于非晶合金晶化的理论研究也备受关注。以往理论研究普遍认为晶化驱动力描述状态，能垒针对过程，从而忽略了两者的关系。然而，越来越多的实验现象表明驱动力与能垒存在内在联系。本项目拟以Fe-B系和Cu-Zr系两种热稳定性不同的二元非晶合金为对象，从微观原子结构出发研究晶化行为。首先，在实验上实现对非晶合金微观原子结构的定量表征；其次，说明微观原子结构同晶化行为的关系，并建立反映驱动力和能垒函数关系的微观速率方程；最后，揭示晶化驱动力、能垒、热力学和动力学性质之间的固有关系，从晶化角度研究非晶合金中热力学性质与动力学性质相关性。本项目可推动晶化理论模型发展，并为深刻理解非晶态物质提供理论依据。

本项目针对Zr基和Fe基非晶合金晶化过程中，晶化驱动力、能垒与非晶合金性质及其原子结构之间的相互关系开展深入研究。主要研究内容有：（1）Cu-Zr与Fe-B非晶合金晶化行为对比研究；（2）Cu-Zr非晶合金在不同温度程序下的晶化行为研究；（3）Zr基非晶合金性质与晶化行为研究；（4）非晶合金结构与其晶化行为关系研究；（5）非晶合金变形对晶化动力学的影响。取得主要研究结果如下：提出了连续降温过程中非晶晶化动力学分析方法；在Cu-Zr非晶合金中，非晶合金中出现的短程有序结构降低了晶化驱动力，并增大了晶化能垒，进而阻碍晶化过程进行，晶化过程体现出非晶合金性质的影响；非晶合金变形后，其原子结构发生改变，进而导致非晶合金的晶化行为异常。通过以上研究，初步建立了非晶合金性质与晶化行为之间的联系，为理解非晶合金结构提供了新思路。