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, Ti0.4Cr0.3Nb0.3O2 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.