Microstructure and Oxidation Behavior of Cr/Mo Modified TiAl Alloy Containing High Nb

In this paper, the microstructure and oxidation behaviour of Ti-45Al-8Nb-0.2Si-0.5W-0.8B, Ti-45Al-8Nb-2Cr-0.2Si-0.5W-0.8B, Ti-45Al-8Nb-2Mo-0.2Si-0.5W-0.8B, Ti-45Al-8Nb-2Cr-2Mo-0.2Si-0.5W-0.8B were studied.The alloys were designed and fabricated via vacuum arc melting in the protection of argon shield. The oxidation experiments were carried out at 1073K for 200h in laboratory air. Microstructure evolution, elemental analysis as well as the composition distribution of the oxide scale were performed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) technique, respectively. The results showed that the microstructure could be refined by adding of Cr and Mo to a smaller grain size.The heat treatment has a good impact on composition homogenization as well as the generation of γ-TiAl phase. The oxidation test shows that Cr and Mo modified alloy cannot improve the oxidation resistance of the alloy. The 0Cr2Mo alloy shows the poorest oxidation resistance in the three, while the Cr modified alloy can apparently slows down the oxidation rate after 50h, which owing to the formation of a compact oxidation scale. (paper)