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

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.