WNbMoTa refractory high entropy alloy (RHEA) with single BCC phase has high strength, high hardness and excellent high-temperature mechanical properties. However, the limited plasticity greatly affects its engineering applications. In this work, WNbMoTaZr_x (x = 0.1, 0.3, 0.5, 1.0) RHEAs were prepared by vacuum arc melting. The microstructure, hardness, compressive properties and fracture behavior were characterized. The results have shown that WNbMoTaZr_x RHEAs have a single BCC1 solid solution phase at low Zr content, and a second BCC2 phase appeared in the RHEAs with a higher Zr content. With the increase of Zr content, the microstructure of WNbMoTaZr_x RHEAs changed to a typical dendrite structure, and simultaneously increase of strength, hardness and compressive plasticity was observed. The improvement of the mechanical properties was mainly attributed to the solid solution strengthening of Zr elements, the formation of more interdendritic regions, and the refinement of dendrite structures. The deformation mechanisms of the RHEAs with increased compressive plasticity were examined using step-by-step observations and discussed related to the evolution of microstructures. The results have shown that under applied loadings, deformation bands were initiated within the dendrite regions, while the propagation of deformation bands was impeded by interdendritic regions, resulting in significantly increased compressive plasticity. The fracture mode also changed from the intergranular fracture in WNbMoTa RHEA to the transgranular fracture in WNbMoTaZr_1.0 RHEA. The present work not only gives more insight into the strengthening and deformation mechanisms of the WNbMoTaZr_x (x = 0.1, 0.3, 0.5, 1.0) RHEAs, but also explores the application potential of WNbMoTa-based RHEAs.

单BCC相的WNbMoTa难熔高熵合金（RHEA）具有高强度、高硬度和优良的高温力学性能。然而，有限的可塑性极大地影响了其工程应用。在这项工作中，通过真空电弧熔化制备了 WNbMoTaZr _x (x = 0.1, 0.3, 0.5, 1.0) RHEA。对其显微组织、硬度、压缩性能和断裂行为进行了表征。结果表明，WNbMoTaZr _x RHEAs在低Zr含量下具有单一的BCC1固溶体相，而在Zr含量较高的RHEAs中出现了第二个BCC2相。随着 Zr 含量的增加，WNbMoTaZr _{x的显微组织}RHEA 转变为典型的枝晶结构，同时观察到强度、硬度和压缩塑性的增加。力学性能的提高主要归功于Zr元素的固溶强化、更多枝晶间区域的形成以及枝晶组织的细化。使用逐步观察检查了具有增加的压缩塑性的 RHEA 的变形机制，并讨论了与微观结构演变有关的问题。结果表明，在外加载荷作用下，枝晶区域内开始产生变形带，而枝晶间区域阻碍了变形带的传播，导致压缩塑性显着增加。_1.0 RHEA。目前的工作不仅更深入地了解了 WNbMoTaZr _x (x = 0.1, 0.3, 0.5, 1.0) RHEA 的强化和变形机制，而且还探索了 WNbMoTa 基 RHEA 的应用潜力。