高温多元合金熔体的物理化学性质及其凝固过程主动控制研究

Extraordinary solidification conditions of high undercoolings combined with a cooling rate or a temperature gradient will be set up by using electromagnetic levitation, glass fluxing, and free fall techniques to conduct the research on the physical and chemical properties and solidification process control of high temperature multi-component alloy melts. Aiming at the characteristics of high temperature and high activity for the melts of titanium alloys and ultra high strength steels in the fields of aeronautics and astronautics, novel measurement methods will be developed by the levitation containerless technique with non-contact manners together with modeling the computational alloy melts, to obtain the physical and chemical properties at both stable and metastable state, including specific heat, surface tension, viscosity, density, solute partition coefficient and Gibbs free energy, etc. In order to find the solidification routes of multi-component alloys, the relationship of topology and chemistry coordination will be studied to realize the component and composition optimization for titanium alloys and ultra high strength steels. Under the control conditions of high undercooling, large cooling rate and huge temperature gradient, the key issues during solidification will be elucidated as follows: free nucleation and directional growth, dendritic growth velocity and grain refining, micro-segregation and solid solubility extension, microstructural morphology and homogenization. To explore the effect of microstructures within titanium alloys and ultra high strength steels on the performances of strength, plasticity, elasticity and corrosion, the correlation among melt properties, solidification process, microstructure and application performances will be clarified. It will be helpful to develop novel control theory and methods of solidification when this project is finished.

本项目采用“电磁悬浮、熔体浸浮、自由落体”等超洁净熔凝技术，建立“深过冷耦合冷却速率和温度梯度调控”的超常凝固条件，探索高温多元合金熔体的物理化学性质及其凝固过程主动控制规律。针对航空航天用钛合金和超强钢熔体“高温、高活性”特征引发凝固过程难以控制的科学难题，发展“无容器非接触”实验测定方法，构建计算物理模型，获取稳定和亚稳态合金熔体的物理化学性质：比热、表面张力、粘度、密度和溶质分配系数等。研究多组元拓扑与化学配位关系，实现钛合金和超强钢组元构成与化学成分优化设计，探明多元复相合金的超常凝固路径。深入研究“深过冷、大冷速、高梯度”及其耦合作用下“自由形核与取向生长、亚稳相形成与稳定性、生长速度与晶粒细化、微观偏析与固溶扩展、组织形态与均质化”等凝固过程控制机理，探索钛合金和超强钢微观组织特征对强度、塑性、弹性和腐蚀等性能的作用机制，揭示“熔体性质—凝固过程—微观组织—应用性能”相关规律。

高温多元合金熔体的物理化学性质及其凝固过程主动控制是钢铁和有色金属冶金、材料制备加工、冶金信息学、电磁冶金学等领域的重要前沿研究课题。本项目在高温多元合金熔体的热物理性质、液态结构和凝固过程主动控制等几方面取得了重要研究进展，包括：(1) 解决了高温合金熔体“高温、高活性”特征引发的物理化学性质难以测定的科学难题，建立了基于“无容器非接触”实验获取高温及难熔合金熔体密度、比热、表面张力、粘度和溶质分配系数等物理化学性质的方法，建立了跨尺度物理化学性质的计算模型，开展了中国空间站在轨合金熔体的热物理性质研究；(2) 发展了利用机器学习开发势函数的方法，建立了评估势函数精确程度的方法，深入分析了多种合金体系短程液态结构随温度及成分变化的演变规律，揭示了液态结构与熔体物理化学性质之间的联系，提出了利用液态结构阐释冷却速率对相选择和竞争形核的影响机制；(3) 在电磁悬浮、静电悬浮、自由落体实验条件下，建立了“深过冷耦合冷却速率、温度梯度调控”凝固过程控制的超常途径。揭示了多元合金的凝固路径与亚稳相形成机理。从而构建了“物理化学性质-液态结构-凝固过程-微观组织”之间的联系。在本项目执行期间，在Acta Mater.、Phys. Rev. E、Metall. Mater. Trans A/B、J. Appl. Phys.等知名期刊发表论文55篇；获得国家发明专利授权11项；获得软件著作权4项。培养博士生17名，硕士生6名。王海鹏教授在2019年获得第十五届中国青年科技奖以及第四批万人计划中青年科技创新领军人才。