Refractory high-entropy alloys (HEAs) exhibit remarkable mechanical properties desired for high-temperature applications. However, their oxidation resistance at high temperatures received less attention. Recent work indicates that MoTaTiCrAl alloy exhibits excellent oxidation resistance, but the effects of Al and Cr remain unclear. In this work, we demonstrate that the addition of Al is unnecessary for preventing oxidation of the MoTaTiCrAl alloy and the removal of Al leads to a more oxidation resistant MoTaTiCr medium entropy alloy. Structural and chemical analyses indicate that the excellent oxidation resistance of MoTaTiCr is mainly associated with the formation of continuous CrTaO₄ oxide layer. The results indicate that complex oxides can be adopted as effective candidates for enhancement of oxidation resistance, in addition to typical strategy of forming Al₂O₃, Cr₂O₃ or SiO₂ barrier layer.

难熔高熵合金（HEA）具有高温应用所需的出色机械性能。但是，它们在高温下的抗氧化性很少受到关注。最近的工作表明，MoTaTiCrAl合金具有优异的抗氧化性，但Al和Cr的作用仍不清楚。在这项工作中，我们证明铝的添加对于防止MoTaTiCrAl合金的氧化是不必要的，而Al的去除会导致MoTaTiCr中等熵合金具有更高的抗氧化性。结构和化学分析表明，MoTaTiCr的优异抗氧化性主要与连续CrTaO ₄的形成有关。氧化层。结果表明，除了形成Al ₂ O ₃，Cr ₂ O ₃或SiO ₂阻挡层的典型策略外，复合氧化物还可以用作增强抗氧化性的有效候选物。