航空发动机 Ti₂AlNb 合金高温氧化行为与失效机理

High-temperature oxidation behavior and failure mechanism of Ti₂AlNb alloy in aircraft engines

摘要

Ti₂AlNb 合金在 650～750 ℃航空发动机典型构件中具有应用潜力，但在复杂高温服役环境下发生氧化脆化。本工作以轧态 Ti₂AlNb 合金为对象、同成分铸态合金为对照，开展 650～800 ℃高温静态氧化 100 h、氧化后室温拉伸及 600～900 ℃高温拉伸性能研究，结合 X 射线衍射仪、扫描电子显微镜、透射电子显微镜/高角环形暗场/扫描透射电子显微镜、电子背散射衍射分析氧化产物、界面结构、元素分布等，阐明轧制组织的氧化损伤和拉伸失效机制。研究结果表明，800 ℃氧化 100 h 后，轧态合金氧化增重为 13.7 mg·cm⁻²，较铸态合金氧化增重（11.3 mg·cm⁻²）提高 21.2%；氧化速率常数由 0.063（铸态合金）增至 0.091（轧态合金），提高 44.4%。轧态合金形成外层混合氧化物、中层 TiO₂ 颗粒层和内层富氧/氮脆化区的多层氧化膜，微裂纹优先在 α₂/O 相界面萌生并沿氧化通道扩展。合金氧化后，室温下，去除氧化层试样断后伸长率由 12.5%（未经氧化）降至 0.7%～5.0%，保留氧化层试样进一步降至 0.4%～0.6%；高温下，温度由 600 ℃升至 900 ℃时，屈服强度由 671 MPa 降至 148 MPa，抗拉强度由 759 MPa 降至 169 MPa，伸长率由 14.1% 升至 161.7%。轧态 Ti₂AlNb 合金拉伸失效由氧化膜开裂、富氧/氮脆化、高温软化等因素共同控制。

Abstract

Ti₂AlNb alloys possess promising application prospects for typical aero-engine components operating at 650-750 ℃, yet they suffer from oxidation embrittlement under the complex high-temperature service environment. In this work, as-rolled Ti₂AlNb alloy is selected as the research material, and as-cast alloy with the identical nominal composition is set as the control group. A series of experiments including 100 h static high-temperature oxidation at 650-800 ℃, room-temperature tensile tests on oxidized specimens, and high-temperature tensile tests at 600-900 ℃ are carried out. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy/high-angle annular dark-field scanning transmission electron microscopy (TEM/HAADF-STEM), and electron backscatter diffraction (EBSD) are employed to characterize oxidation products, interfacial structures, and elemental distribution, so as to clarify the oxidation damage and tensile failure mechanisms of the as-rolled microstructure. The results reveal that after 100 h oxidation at 800 ℃, the mass gain of the rolled alloy reaches 13.7 mg·cm⁻², which is 21.2% higher than that of the as-cast alloy (11.3 mg·cm⁻²). The oxidation rate constant increases from 0.063 for the as-cast alloy to 0.091 for the rolled alloy, representing an increment of 44.4%. A multi-layer oxide scale forms on the rolled alloy, consisting of an outer mixed oxide layer, a middle TiO₂ particle layer and an inner oxygen/nitrogen-enriched embrittlement zone. Microcracks preferentially nucleate at α₂/O phase boundaries and propagate along oxidation channels. After oxidation, at room temperature, the elongation of specimens with oxide layer removed decreases from 12.5% (unoxidized state) to 0.7%-5.0%, while specimens retaining intact oxide layer exhibit a further drop in elongation to 0.4%-0.6%. At high temperature, as the temperature rises from 600 ℃ to 900 ℃, the yield strength declines from 671 MPa to 148 MPa, the ultimate tensile strength decreases from 759 MPa to 169 MPa, and the elongation increases from 14.1% to 161.7%. The tensile failure of as-rolled Ti₂AlNb alloy is jointly governed by oxide layer cracking, oxygen/nitrogen-enriched embrittlement and high-temperature softening.

关键词

Ti₂AlNb 合金 / 高温氧化 / 氧化层结构 / 拉伸性能 / 失效机理

Key words

Ti₂AlNb alloy / high-temperature oxidation / oxide layer structure / tensile property / failure mechanism

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基金资助

国家自然科学基金(U2141222)

国家自然科学基金(52271012)

国家重点研发计划(2025YFE0115300)