The effect of boron (B) addition on the microstructure and mechanical properties of a refractory high-entropy alloy (RHEA) was investigated. The Al_0.1CrNbVMo RHEA was doped with 0.015 at.% of B by the powder metallurgical process, and its mechanical properties were compared with undoped RHEA. The microstructures of the undoped and doped RHEAs consisted of a single body-centered cubic matrix phase with homogeneously distributed Al₂O₃ inclusions. The doped B atoms segregated along grain boundaries and did not form any boride phases. Boron segregation at the grain boundaries was characterized by atom-probe tomography. Compared with the undoped RHEA, the B-doped RHEA showed improved yield strength of 2933 MPa (15% improvement) and ductility of 25.9% (26% improvement). Adding B transformed the fracture surface from intergranular to transgranular due to enhanced grain boundary cohesion induced by B segregation, which resulted in improved ductility. Quantitative analysis was conducted on the undoped and doped alloys to investigate the effect of B on yield strength. The improved yield strength resulting from B doping was attributed to the combined effects of Orowan, dislocation, and B interstitial strengthening. This work demonstrates that B doping of RHEAs is a promising way to overcome their limited room temperature ductility, while maintaining excellent strength.

研究了硼 (B) 添加对难熔高熵合金 (RHEA) 显微组织和机械性能的影响。Al _0.1 CrNbVMo RHEA 通过粉末冶金工艺掺杂了 0.015 at.% 的 B，并将其机械性能与未掺杂的 RHEA 进行了比较。未掺杂和掺杂的 RHEA 的微观结构由具有均匀分布的 Al ₂ O ₃的单一体心立方基体相组成夹杂物。掺杂的 B 原子沿晶界分离，没有形成任何硼化物相。晶界处的硼偏析通过原子探针层析成像来表征。与未掺杂的 RHEA 相比，B 掺杂的 RHEA 的屈服强度提高了 2933 MPa（提高了 15%），延展性提高了 25.9%（提高了 26%）。由于 B 偏析引起的晶界内聚力增强，添加 B 使断裂表面从晶间转变为穿晶，从而提高了延展性。对未掺杂和掺杂的合金进行了定量分析，以研究 B 对屈服强度的影响。B 掺杂导致屈服强度的提高归因于 Orowan、位错和 B 间隙强化的综合作用。