Refractory high-entropy alloys (RHEAs) are sensitive to thermal oxidation, significantly restricting their service performance and potential applications. However, the wet oxidation behavior of RHEAs has remained poorly understood despite the potential risk of catastrophic oxidation caused by water vapor. In this study, the oxidation mechanism of an equiatomic TiZrHfNbTaV high-entropy alloy (HEA) has been investigated in a wet atmosphere at elevated temperatures. Synchronous oxidation of all elements occurs at temperatures below 800 °C. At temperatures above 800 °C, preferential oxidation of Nb, Ti, and Zr, and internal oxidation of V occur on HEAs, which are thermodynamically less preferred as compared with oxidations of more reactive Hf and Ta. Experimental and theoretical analyses show that the oxide grain boundaries and substrate interdendritic regions of HEAs act as diffusion pathways for V and oxidizing species during preferential and internal oxidation processes. This work provides a fundamental understanding of the oxidation of multicomponent alloys in wet environments, which is helpful in the development of effective oxidation resistance strategies and innovative surface engineering techniques.

中文翻译：

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TiZrHfNbTaV 高熵合金的湿式氧化：晶界和枝晶间扩散的作用

难熔高熵合金（RHEA）对热氧化敏感，严重限制了其使用性能和潜在应用。然而，尽管水蒸气存在引起灾难性氧化的潜在风险，但人们对 RHEA 的湿氧化行为仍然知之甚少。在这项研究中，研究了等原子 TiZrHfNbTaV 高熵合金 (HEA) 在高温潮湿气氛中的氧化机制。所有元素的同步氧化发生在温度低于 800 °C 时。在高于 800 °C 的温度下，Nb、Ti 和 Zr 的优先氧化以及 V 的内部氧化发生在 HEA 上，与更具反应性的 Hf 和 Ta 的氧化相比，这在热力学上不太优选。实验和理论分析表明，HEA 的氧化物晶界和基底枝晶间区域在优先氧化和内部氧化过程中充当 V 和氧化物质的扩散路径。这项工作提供了对潮湿环境中多元合金氧化的基本了解，有助于开发有效的抗氧化策略和创新的表面工程技术。