Microstructure and High-Temperature Oxidation Behavior of Dy-Doped Nb–Si-Based Alloys

Microstructures and oxidation behaviors of four Dy-doped Nb–Si-based alloys at 1250 °C were investigated. The nominal compositions of the four alloys are Nb–15Si–24Ti–4Cr–2Al–2Hf–xDy (at.%), where x = 0, 0.05, 0.10 and 0.15, respectively. Results showed that the four alloys all consisted of Nbss, αNb₅Si₃ and γNb₅Si₃, and the addition of Dy produced no obvious effect on the phase constitution and the microstructures of Nb–Si-based alloys. After oxidation at 1250 °C for 58 h, it was found that the addition of Dy accelerated the oxidation rate of Nb–Si-based alloys and caused a larger weight gain, accompanied by the formation of a more porous and less protective oxide scale. The oxides of Nb₂O₅, Ti₂Nb₁₀O₂₉, TiNb₂O₇, Ti_0.4Cr_0.3Nb_0.3O₂ and glassy SiO₂ were formed on Dy-doped Nb–Si-based alloys. The high-temperature oxidation mechanism of Dy-doped Nb–Si-based alloys was discussed.