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

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.