共晶多主元合金兼备了共晶合金良好的可加工性和多主元合金因高熵效应引起的优异综合性能。 通过耦合多种组织调控手段，其有望表现出更丰富的组织形貌特点，性能潜力得以进一步发掘。 基于此，采用静磁场辅助深过冷凝固技术，系统研究了 2T 磁场作用下 FeCoNiB0.65 共晶多主元合金的非平衡凝固行为与组织演化规律。 结果表明，随过冷度增加，初生组织由 α-M 枝晶转变为海藻状的共晶型枝晶，且组成海藻的两相经历了从 α-M/M23B6 到 α-M/M3B 的相转变；凝固组织中的基体呈现出 M3B 相与 M23B6 相频繁的相竞争现象，这与两相凝固时所需要克服的临界形核势垒有关， 对于 ΔT=60 K 时基体中两相共存的特征则与不完全的 M23B6 相分解形成 M3B 的固态相变有关；M23B6 相与 α-M相均为 FCC 结构，且两相表现出显著的耦合生长特性，在凝固过程中可以形成一种 cube-cube 取向关系。

Eutectic multi-principal element alloys combine the good workability of eutectic alloys with the excellent comprehensive properties caused by the high-entropy effects of multi-principal element alloys. By coupling various microstructure regulation methods, more diverse microstructural characteristics are expected to be exhibited, and its performance potential can be further explored. On the basis of this, static magnetic field and deep undercooling technology were combined to systematically investigate the non-equilibrium solidification behavior and microstructural evolution law of the FeCoNiB0.65 alloy. The results demonstrate that with increasing undercooling, the primary structure undergoes a morphological transition from α-M dendrites to seaweed-like eutectic dendrites, and the two phases inside the seaweed transition from α-M/M23B6 to α-M/M3B. The alloy matrix frequently experiences competitive formation between the M23B6 phase and the M3Bphase, which is related to the critical nucleation barrier that needs to be overcome during solidification. The coexistence of two phases in the matrix at ΔT=60 K is related to the solid-state phase transition from incomplete decomposition of the M23B6 phase to the M3Bphase. Both the M23B6 and α-M phases have FCC crystal structures and exhibit significant coupled growth characteristics, forming a cube-cube orientation relationship during solidification.