稀土Y对含锰β凝固γ-TiAl合金高温氧化行为影响

Influence of Rare Earth Y on High-Temperature Oxidation Behavior of Mn-Containing β-Solidified γ-TiAl Alloys

摘要:

以低成本、易变形Ti44Al3Mn0.4W0.4Mo0.1B0.1C（TMMW）合金为研究对象，分析微量稀土元素Y对TMMW合金800 ℃高温抗氧化能力的影响。采用EPMA、XRD和TEM等分析手段对合金显微组织和氧化膜进行了系统表征，同时分析了Y对合金高温抗氧化性影响的内在机理。结果表明，微量Y添加会对合金显微组织产生一定影响，采用相同热处理制度后，无Y合金主要由γ、α₂、β_o三相组成，而含Y合金不仅含有γ、α₂、β_o相，在片层边界和内部另外析出YAl₂相和较少的Y₂O₃。循环氧化动力学实验表明，两种合金表面氧化膜结构均为TiO₂/Al₂O₃/TiO₂+Al₂O₃ 3层复合结构，过渡层主要为TiMn₂-Laves和少量富含Mo和W元素的β_o相。0.3at%Y的加入可以减少TMMW合金氧化增重并提高氧化皮的抗剥落能力，同时明显减少过渡层中β_o相含量。

Abstract:

The influence of trace amounts of rare earth element Y on the high-temperature oxidation resistance was investigated for low-cost and easily deformable Ti44Al3Mn0.4W0.4Mo0.1B0.1C(TMMW) alloy at 800 °C. The microstructure and oxide film of the alloy were analyzed using EPMA, XRD, and TEM, and the underlying mechanisms of element Y affecting the high-temperature oxidation resistance of the alloy were explored. Results indicate that the addition of a trace amount of Y exerts a certain impact on the microstructure of the alloy. After identical heat treatment, the Y-free alloy primarily consists of γ, α₂, and β_o phases, whereas the Y-containing alloy not only contains these phases but also exhibits precipitation of the YAl₂ phase at lamellar boundaries and within the matrix, with minimal formation of Y₂O₃. Cyclic oxidation kinetics tests reveal that the oxide film formed on both alloys comprises a three-layer composite structure: TiO₂/Al₂O₃/TiO₂+Al₂O₃, with the transition layer mainly composed of TiMn₂-Laves phase and a small quantity of Mo- and W-rich β_o phase. The addition of 0.3at%Y effectively reduces oxidation mass gain, enhances spallation resistance of the oxide scale, and significantly decreases the βo phase content in the transition layer.