Abstract
The microstructures and oxidation behavior of the NbSiTiAlHf alloys doped with rare earth elements at 1300 °C were investigated. The nominal compositions of the selected alloys are Nb-13.5Si-23Ti-37Al-5Hf-0.5X (at.%), where X = Y, Dy, and La, respectively. It was shown that the whole scales were mainly composed of the major phases of Al(2)O(3) and the minor phases of TiO(2), where the TiO(2) formed on the surface or in the upper layer of scales, for the undoped, Y, and Dy-doped alloy. But, for the 0.5 at.% La-doped alloys, the whole scales were constituted with the major phases of both Al(2)O(3) and TiO(2), and contained plenty of large voids. The 0.5 at.% Dy-doped alloys exhibited the lowest scale growth rate with the value of 1.87 × 10(-11) cm(2)/s, and the benefits of Y on the oxidation rates were short-term, while 0.5 at.% La-doped alloys had the highest scale growth rate of 4.55 × 10(-10) cm(2)/s compared with those of all the selected alloys. Then, the effects of Y, Dy, and La on the oxidation behavior of the alumina-scale-forming NbSiTiAlHf alloys were discussed.