小平面包晶合金糊状区凝固行为的同步辐射原位研究

The microstructure evolution of the mushy zone plays a critical role in the directional solidification of faceted peritectic alloy. The growth mechanism, migration kinetics and 3D morphology evolution of intermetallic compounds and liquid inclusions (liquid channels and droplets) is the key fundamental for controlling the microstructure of the mushy zone. However, the theory of microstructural development during peritectic solidification is based on the non-faceted peritectic alloys, which is not completely suitable for faceted peritectic alloys. In the present study, the solute distribution, migration of droplet and interface in the mushy zone of faceted peritectic alloy will be dynamically observed by using synchrotron radiation X-ray phase contrast and K-edge subtraction imaging technology, the 3D morphology evolution of intermetallic compounds, droplets and interface will be continuously characterized by in-situ 4D quantification, and the data will be optimized and analyzed by using machine learning particle tracking algorithm. This study focuses on the 3D morphology evolution and interaction mechanism of intermetallic compounds and liquid channels in the mushy zone. Then, the relationship between the geometric shape and migration behavior for the droplets will be figured out. In addition, the interaction of solute distribution, compounds morphology and interfacial migration at the interfaces will be revealed. It is of great importance to analyze the theoretical base in order to effectively control the microstructure in directionally solidified peritectic alloy with faceted phases.

小平面包晶合金糊状区组织对最终定向凝固组织产生重要影响。金属间化合物与液相夹杂（液相通道与液滴）的生长、迁移及空间形态演变机理是调控糊状区组织的关键理论基础。然而，目前相关的相选择与生长机制等包晶凝固理论是以固溶体型非小平面包晶体系为研究对象而建立的，并不完全适用于小平面包晶合金。本项目拟选择小平面包晶体系，通过同步辐射X射线二维相位衬度与K边减影成像技术对其糊状区溶质分布、液滴及交界面迁移行为进行动态观察，利用原位4D表征对金属间化合物、液相夹杂及交界面空间形态演变进行连续表征，并借助机器学习粒子跟踪算法实现数据优化与分析。研究糊状区金属间化合物与液相通道的空间形态演变及交互作用机制，弄清液滴几何形态与迁移行为的相关性，揭示不同糊状区交界处溶质分布、金属间化合物生长形态及界面迁移行为的相互影响规律，为实现小平面包晶合金定向凝固组织的有效调控提供理论依据。

阐明小平面金属间化合物、液相夹杂与气泡的生长、迁移与形态演变机理对调控含小平面化合物合金的凝固组织与性能产生重要影响。本项目主要通过同步辐射X射线二维成像技术与微观断层扫描技术相结合，定量地研究含小平面化合物合金的非均质溶解与凝固机制。实现了凝固过程中小平面金属间化合物、液相夹杂与气泡生长行为与形态演变的动态表征，揭示了多晶相的非均质溶解行为与界面形貌转变机理，明晰了小平面金属间化合物的复杂三维形态、形成与生长机制，建立了液相夹杂与氢气泡的几何形态演变与迁移动力学，构建界面金属间化合物的交互生长与临界生长厚度的数理模型，阐明小平面化合物的交互作用与表面凹槽形成机理；为含小平面化合物相合金糊状区凝固组织的调控提供理论依据，进一步丰富和发展含小平面金属间化合物合金的凝固理论。基于以上研究，以第一作者发表SCI学术论文9篇，申请发明专利1项，项目主持人入选佛山市领军人才与上海交通大学晨星博士后激励计划。