fcc/bcc沉淀相变系统相界面的精细结构及迁移过程的实验及理论研究

沉淀相和基体之间的相界面是相变发生的前沿，其迁移性质对沉淀相形貌的演化起决定性的影响。界面的迁移性与其原子尺度精细结构密切相关。在原子尺度上对界面结构及其迁移性质的定量认识，是正确理解和计算预测沉淀相形貌的重要基础。目前，这方面基础知识还十分欠缺。为了加深对沉淀相形貌的定量理解，本项目拟对fcc/bcc相变体系中相界面的精细结构和迁移性质进行系统的实验表征和原子尺度模拟。在实验方面，将使用透射电镜对Ni-Cr合金和双相不锈钢中相界的界面结构和迁移特性进行精确测量。在理论方面，将应用原子尺度模拟系统计算不同取向界面的原子结构并模拟界面迁移的具体过程；分析生长台阶的形核和迁移过程；考察界面的迁移模式并探索其受驱动力的影响；研究界面迁移-切变的耦合现象。综合实验和模拟结果，建立理论和实验自洽的界面迁移模型，完善沉淀相变组织形成理论。

The migration properties of interfaces between precipitates and their matrix play a decisive role in the morphology evolution of the precipitates, since the interfaces are the front of transformation. The migration properties of an interface are closely related to the fine structure of the interface on the atomic scale. Therefore, quantitative descriptions of the atomistic structures and migration properties of the interfaces is essential for correct interpretation and prediction of precipitate morphology. At present, however, the knowledge of interfaces on this subject is rather limited. In order to improve in-depth understanding of precipitation morphology, it is proposed in this project to make a systematic investigation on the fine structures and migration characteristics of interfaces in fcc/bcc phase transformation systems. A Ni-Cr alloy and a duplex stainless steel will be used as model alloys for the study of structures and migration properties of interfaces with transmission electron microscopy. Atomistic simulations will be applied to calculate the atomic structures of interfaces at different orientations around a precipitate and to simulate the migration of interfaces. The nucleation and migration process of growth ledges, the migration modes of different interfaces and their correlation with the driving force,and the shear-coupled interface motion will be systematically investigated. Based on the integrated results from experiments and simulations, an interface migration model that is consistent with both experiments and simulations will be developed, and hence the microstructure formation theory on precipitation will be improved.