NbTiZrV alloy is one of the lightweight refractory high-entropy alloys (RHEAs) and has a great potential to be structural materials. Here, the microstructural evolution at the grain boundaries (GBs), the tensile properties and the deformation mechanism including dislocation and kink evolution of arc-melting (NbTiZrV)Ce RHEAs (at.%, = 0, 0.005, 0.01, referred to as 0Ce, 0.005Ce and 0.01Ce alloys) at room temperature (RT) were systematically investigated. Ce was found to segregate at GBs and the most pronounced grain refinement effect in the 0.005Ce sample. With the Ce content increased from 0.005 at.% to 0.01 at.%, the Ce concentration at GBs increased from 0.12 at.% to ∼1.17 at.%, subsequently, inducing compositional fluctuation and facilitating transformation of BCC band (V-rich but Zr-poor) to ω-like phase with a non-close-packed hexagonal structure (NCPHS, V- and Zr-rich but Ti-poor) at GBs. The 0.005Ce alloy exhibited the optimized ductility (∼7.15%) and maintained yield strength of approximately 964 MPa at RT. The better balance of strength-ductility in the 0.005Ce alloy was resulted from synergistic deformation of multiple grains, high fraction (55.6%) of movable edge dislocations and abundant kink bands with the most slip systems. However, deteriorating ductility (∼2.29%) of the NbTiZrV alloy with 0.01 at.% Ce addition was mainly attributed to precipitation of the brittle ω-like phase at GBs. These results may provide theoretical and experimental guidance for design of the advanced RHEAs with high specific strength through doping Ce or other rare-earth elements.

中文翻译：

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Ce掺杂Nb0.5TiZrV0.5难熔高熵合金室温晶界演化及变形机制

NbTiZrV合金是轻质难熔高熵合金（RHEAs）之一，具有巨大的结构材料潜力。此处，晶界 (GB) 处的微观结构演化、拉伸性能和变形机制，包括电弧熔炼 (NbTiZrV)Ce RHEA (at.%, = 0, 0.005, 0.01，简称 0Ce) 的位错和扭结演化、0.005Ce 和 0.01Ce 合金）在室温 (RT) 下进行了系统研究。发现 Ce 在 GB 处偏析，并且在 0.005Ce 样品中晶粒细化效果最明显。随着Ce含量从0.005 at.%增加到0.01 at.%，GBs处的Ce浓度从0.12 at.%增加到~1.17 at.%，随后引起成分波动并促进BCC带（富V但贫 Zr）到 GB 处具有非密排六方结构（NCPHS，富 V 和 Zr，但贫 Ti）的类 ω 相。 0.005Ce 合金表现出优化的延展性 (∼7.15%)，并在室温下保持约 964 MPa 的屈服强度。 0.005Ce合金具有更好的强度-延展性平衡，这是由于多晶粒的协同变形、高比例（55.6%）的可动刃位错以及具有最多滑移系统的丰富的扭结带。然而，添加 0.01 at.% Ce 的 NbTiZrV 合金的延展性恶化（~2.29%）主要归因于晶界处脆性类 ω 相的析出。这些结果可以为通过掺杂Ce或其他稀土元素设计具有高比强度的先进RHEA提供理论和实验指导。