多主元高熵合金因性能优异而被广泛研究，但其粗大柱状晶凝固组织是亟待解决的典型难题之一。探明多主元合金凝固过程的溶质传输行为和柱状晶-等轴晶转变(CET)的诱导因素及作用机理，对于多主元合金晶粒细化至关重要。前期研究发现，在CrMnFeCoNi系多主元合金中添加B、C等元素对促进CET转变和晶粒细化十分有效。基于此，本项目从凝固界面前沿溶质间交互作用行为与机制入手，系统研究其诱导CET转变和晶粒细化的内在机理。主要开展以下研究：1）具有强交互作用和偏析特征溶质（用X和Y表示）的配分行为与机制；2) CrMnFeCoNi-X-Y体系凝固界面前沿扩散边界层的溶质交互作用；3）溶质交互作用诱导CET和晶粒细化的综合理论模型；4）溶质交互作用诱导大尺寸铸锭晶粒细化的机理分析。本项目研究既针对CrMnFeCoNi系的典型问题，亦可为其它多主元合金及细晶方法提供新思路和理论基础。

The multi-principal-element high-entropy alloys have been investigated extensively due to their excellent properties, however, their coarse columnar-grained solidification structures have become a typical issue which needs to be solved urgently. It is of great importance to understand deeply the solute transport behavior and inducing factors of columnar to equiaxed grain transition (CET) of multi-principal-element alloys with the aim to improve their grain refinement. The previous work indicated that the alloying of B, C and other elements is effective for the CET and grain refinement of CrMnFeCoNi system multi-principal-element alloys. Thus this project will base on the solute interaction ahead of the solidification interface and systematically investigate its mechanism on the CET and grain refinement. The researches mainly include: 1) Partition behavior and mechanism of the alloying solutes (denoted as X and Y) with strong mutual interaction and segregation features; 2) The solute interaction in the diffusion boundary layer ahead of the solid-liquid interface of the CrMnFeCoNi-X-Y system during solidification; 3) The integrated theory model of the CET and grain refinement induced by solute interaction; 4) The mechanism analysis of solute interaction effect on grain refinement of large-sized cast ingots. This project is of great significance in the solution to the typical issue of CrMnFeCoNi system multi-principal-element alloys and will provide new methods and theoretical foundation for other multi-principal-element systems and other grain refinement approaches.