稀土Y对含锰β凝固γ-TiAl合金高温氧化行为影响

The influence of rare earth Y on the high-temperature oxidation behavior of Mn-containing β-solidified γ-TiAl alloys

摘要:

本文以低成本、易变形TMMW(Ti44Al3Mn-0.8(W,Mo)-(B,C))合金为研究对象,研究微量稀土元素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+ Al₂O₃三层复合结构,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:

This study investigates the influence of trace amounts of rare earth element Y on the high-temperature oxidation resistance of a low-cost and easily deformable TMMW (Ti44Al3Mn-0.8(W,Mo)-(B,C)) alloy at 800°C. The microstructure and oxide scale formation of the alloy were systematically analyzed using EPMA, XRD, and TEM techniques, and the underlying mechanisms by which Y affects the oxidation resistance were explored in detail. Experimental results indicate that the addition of trace Y exerts a notable effect on the alloy"s microstructure. After identical heat treatment, the Y-free alloy primarily consists of γ, α₂, and β_o phases, whereas the Y-containing alloy not only retains 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 scale 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 0.3 at.% Y effectively reduces oxidation weight gain, enhances spallation resistance of the oxide scale, and significantly decreases the βo phase content in the transition layer.