基于同步辐射成像与相场模拟宏-微观原位耦合的高性能Mg-Gd-Zr系合金非平衡凝固动力学及组织调控研究

高性能Mg-RE合金中，凝固组织形貌及形态转变的定量调控是提升高温强度和蠕变抗力的重要手段之一。本项目将从不同凝固参数下Mg-Gd-Zr系合金的非平衡凝固入手，利用凝固特征长度与界面能的Oldfield关系，将同步辐射成像和相场模拟进行宏-微观原位耦合，针对凝固枝晶生长特征及晶型转变的定量表征和微观演化的动力学调控两个关键科学问题，深入研究Mg-Gd-Zr合金凝固过程中的枝晶生长及晶型转变，从热力学和动力学角度诠释温度梯度、冷速及成份对枝晶尖端半径、生长速率、枝晶生长取向及溶质偏析的影响机制；明确温度与枝晶晶型转变的量化关系，构建枝晶晶型-温度的转变图；建立适用于Mg-Gd-Zr系合金非平衡凝固的相场模拟平台，揭示不同溶质含量及温度条件下枝晶形核、生长及晶型转变的微观动力学机理，实现凝固组织形貌及形态转变的定量调控和预测，为低成本、高效率开发高性能Mg-RE合金提供理论指导。

In the high-performance Mg-RE alloy, the quantitative regulation of solidification microstructure and morphology transformation is one of the critical approaches to improve its high-temperature strength and creep resistance. This project will start with the non-equilibrium solidification of Mg-Gd-Zr alloy under different solidification parameters. We will investigate two crucial scientific problems, the quantitative characterization of dendritic growth and crystal transformation, and the dynamic control of microstructure evolution, macro-micro in-situ coupling synchrotron radiation imaging and phase field simulation by using Oldfield relation between solidification characteristic length and interface energy, We will, 1) analyze the mechanism and role of the temperature gradient, cooling rate and composition in influencing dendrite tip radius, growth rate and growth orientation from both thermodynamic and kinetic perspective; 2) quantify the temperature and dendrite crystal transformation relationship, and establish the transformation diagram of the dendrite crystal structure vs temperature; 3) construct a phase-field model for the non-equilibrium solidification of Mg-Gd-Zr alloys to reveal the microscopic kinetic mechanism for dendrite nucleation, growth, and crystal transformation under various solute concentration and temperature conditions，aiming to achieve quantitative control and prediction of solidification microstructure morphology and morphological transition. This project will lead to both data support and theoretical guidance for the cost-effective and efficient development of high-performance Mg-RE alloys.