难熔高熵合金(RHEAs)具有高热稳定性、良好的高温力学性能和优异的高温抗氧化性能，有望作为一种潜在的耐高温结构材料使用。为了降低RHEAs密度、改善其高温抗氧化性能，本工作向CrNbTiV合金中添加Al元素，制备了一系列CrNbTiVAl _x (x = 0.25、0.5、0.75、1.0)难熔高熵合金。采用XRD、SEM、EDS和电子万能试验机等手段研究Al含量对CrNbTiV难熔高熵合金微观组织、力学性能和高温氧化行为的影响规律。结果表明，CrNbTiVAl _x 合金的微观组织由bcc、Laves和α-Ti相组成，bcc相以等轴晶形式分布。随着Al含量的增加，合金的密度逐渐减小，屈服强度由2037 MPa降低至1371 MPa；比屈服强度由CrNbTiVAl_0.75合金的215.93 MPa·cm³/g增加至CrNbTiVAl_0.25合金的323.33 MPa·cm³/g。CrNbTiVAl _x 合金在900 ℃氧化时的氧化动力学遵循抛物线规律，增加Al含量有利于提高合金的高温抗氧化性能。CrNbTiVAl _x 合金氧化后的氧化产物是由Al₂O₃、(CrNbTiVAl)O₂和VO _x 组成的混合结构。当Al含量较低时，合金表面形成的连续、紧密的复杂氧化物(CrNbTiVAl)O₂有效阻止了O₂向基体内的扩散。随着Al含量的增加，复杂氧化物(CrNbTiVAl)O₂含量减少，表面形成了更加致密、连续且细小的Al₂O₃氧化膜，从而显著提高了合金的高温抗氧化性能。

Owing to their high thermal stability, good high-temperature mechanical properties, and excellent high-temperature oxidation resistance, refractory high-entropy alloys (RHEAs) are strong candidates for structural materials in high-temperature applications. To reduce the density and improve the high-temperature oxidation resistance of RHEAs, in this study, the Al element was added into CrNbTiV alloys, forming a series of CrNbTiVAl _x RHEAs (x = 0.25, 0.5, 0.75, 1.0). The effects of Al content on the microstructure, mechanical properties, and high-temperature oxidation behaviors of the CrNbTiV RHEAs were studied using XRD, SEM, EDS, and an electronic universal testing machine. A mixture of bcc, Laves, and α-Ti phases was found in the CrNbTiVAl _x RHEAs and equiaxed grains were observed in the bcc phase. Increasing the Al content decreased the density of the alloys and reduced the yield strength from 2037 to 1371 MPa. The specific yield strength ranged from 215.93 MPa·cm³/g in CrNbTiVAl_0.75 to 323.33 MPa·cm³/g in CrNbTiVAl_0.25. After oxidation at 900 ^oC, the CrNbTiVAl _x RHEAs exhibited parabolic oxidation kinetics and their high-temperature oxidation resistance was improved due to increased Al content. The oxidized products were determined as Al₂O₃, (CrNbTiVAl)O₂, and VO _x. The surfaces of the alloys with low Al content formed a continuous and compact complex oxide (CrNbTiVAl)O₂ that effectively prevented the diffusion of O₂ into the substrate. Increasing the Al content decreased the amount of complex oxide (CrNbTiVAl)O₂, forming denser, continuous, and finer Al₂O₃ oxides on the surface that appreciably improved the high-temperature oxidation resistance.