NbMoTaW refractory high-entropy alloys (RHEAs) possess superior high-temperature mechanical strength. However, their practical applications are limited by low room-temperature plastic strain. In the present study, NbMoTaW (x = 0.2, 0.4, 0.6, 0.8, 1.0) RHEAs were prepared. The microstructural characteristics, mechanical properties and oxidation resistance of these RHEAs were investigated. The NbMoTaW RHEAs were all single-phase solid solutions. With the addition of W content, the yield strength, density and hardness of the alloy gradually increased, and the grain size decreased. Notably, a significant improvement in the compressive ductility of the investigated NbMoTaW RHEAs was observed. The highest mechanical strength (1712 MPa) and ductility (10.6 %) were exhibited by NbMoTaW. Fracture surfaces indicate the alloy fractured along the grain. The W can be solidly dissolved in the Nb and Ta oxides, altering the structure of the oxide to impede the entry of oxygen and slow down the rate of oxidation. The increase of W enhanced the oxidation resistance of the alloys.

中文翻译：

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NbMoTaWx难熔高熵合金的力学性能和氧化行为

NbMoTaW 难熔高熵合金（RHEA）具有优异的高温机械强度。然而，它们的实际应用受到低室温塑性应变的限制。在本研究中，制备了 NbMoTaW (x = 0.2、0.4、0.6、0.8、1.0) RHEA。研究了这些 RHEA 的微观结构特征、机械性能和抗氧化性。 NbMoTaW RHEA 均为单相固溶体。随着W含量的增加，合金的屈服强度、密度和硬度逐渐提高，晶粒尺寸减小。值得注意的是，所研究的 NbMoTaW RHEA 的压缩延展性显着提高。 NbMoTaW 表现出最高的机械强度（1712 MPa）和延展性（10.6%）。断裂面表示合金沿晶粒断裂。 W可以牢固地溶解在Nb和Ta的氧化物中，改变氧化物的结构，阻止氧的进入并减慢氧化速度。 W的增加增强了合金的抗氧化能力。