Effect of Zr on microstructure and oxidation behavior of α and α + α2 Ti-Al-Nb alloys

Abstract

To develop high-temperature Ti alloys, microstructure and oxidation behavior were investigated in Ti-(10,15)Al-2Nb-(1,2)Zr (at%) alloys. For reference, ternary Ti-15Al-2Zr alloy was also investigated. A single α phase exists in Ti-10Al-2Nb-(1, 2)Zr alloys; on the other hand, an α and α2 two-phase was observed in Ti-15Al-2Nb-(1, 2)Zr alloys. Fine α2 precipitates of about 10 nm were observed in the Ti-15Al alloys. The oxidation behavior of Ti-Al-Nb-Zr and Ti-Al-Zr ternary alloys was investigated to understand the effect of Zr on oxidation behavior at 1023 K. It was found that Zr improves the oxidation resistance of the α phase more effectively than Nb. TiO2 was formed in all tested alloys. The addition of Zr drastically decreased the growth rate of TiO2. It was also found that the addition of Nb improved adhesion of the oxide layer.