成分过冷诱导异质形核作用下的激光沉积高熵合金晶粒等轴细化机理

激光沉积技术具有急热快冷的特点，可大幅降低高熵合金材料中的宏观偏析，有望成为制备高熵合金材料的理想方法。然而激光沉积高熵合金易产生粗大柱状晶组织，限制了该技术在高熵合金制备中的广泛应用。本项目充分利用成分过冷促进柱状晶/等轴晶生长转变，同时又能强化异质形核细晶效果的特性，提出通过激光沉积高熵合金成分调控，增加固/液界面前沿成分过冷度，同时诱导异质形核，制备出细小等轴晶组织高熵合金。项目从高熵合金成分体系多主元特点的角度出发，探索高熵合金相形成规律预测参数与生长限制因子间的关联，阐明激光沉积高熵合金成分过冷的调控机制；基于成分过冷对有效异质形核粒子比例的影响，揭示成分过冷下异质形核行为的调控机理，建立成分过冷诱导异质形核作用下的激光沉积高熵合金晶粒等轴细化理论。本项目的顺利实施将有助于进一步认识成分过冷对激光沉积高熵合金晶粒形貌的影响机理，为激光沉积高性能高熵合金的工业化应用奠定理论基础。

Laser deposition technology possesses the characteristics of rapid heating and cooling, which can significantly reduce the macrosegregation in high entropy alloys, and is expected to become an ideal method for the preparation of high entropy alloys. However, coarse columnar grains of high entropy alloys obtained by laser deposition limit its wide application in the preparation of high entropy alloys. This project makes full use of the advantages of constitutional supercooling in promoting the columnar to equiaxed transition and enhancing the grain refinement effect of heterogeneous nucleation. It is proposed that the constitutional supercooling ahead of the solid/liquid interface can be promoted by adjusting the composition of high entropy alloys prepared by laser deposition, which in turn contributes to the emergence of the heterogeneous nucleation events. Considering the characteristics of multi-principal elements in high entropy alloys, this project clarifies the regulation mechanism of constitutional supercooling in laser deposited high entropy alloy by establishing the relationship between the parameters for phase formation prediction of high entropy alloys and the growth restriction factor. Based on the effect of constitutional supercooling on the proportion of active heterogeneous nucleation particles, the regulation mechanism of heterogeneous nucleation under the influence of constitutional supercooling. Finally, this project establishes the grain equiaxing and refining theory in laser deposited high entropy alloy under the effect of constitutional supercooling induced heterogeneous nucleation. The implementation of this project will contribute to the further understanding of the influence mechanism of constitutional supercooling on the grain morphology of laser deposited high entropy alloys, and providing the theoretical basis for the industrialization of laser deposited high performance high entropy alloys.