Core-multishell globular oxidation in a new TiAlNbCr alloy at high temperatures

Oxidation resistance is one of key properties of titanium aluminide (TiAl) based alloys for high-temperature applications such as in advanced aero-engines and gas turbines. A new TiAlNbCr alloy with micro-addition of yttrium has been developed, but its oxidation behavior is unknown. To provide some fundamental insights, high-temperature oxidation characteristics of this alloy are examined via scanning electron microscopy, transmission electron microscopy, electron probe microanalysis, and X-ray diffraction. We show that distinctive core-multishell globular oxidation and “daisy” flower-like oxidation occur exclusively around Y(2)O(3) particles. Globular oxides exhibit multi-layered Y(2)O(3)/TiO(2)/Al(2)O(3)-rich/TiO(2)-rich shell structures from the inside to outside. Flower-like inner oxides consist of core Y(2)O(3) particles surrounded by divergent Al(2)O(3) and oxygen-rich α(2)-Ti(3)Al in the near-scale substrate. As the scale-substrate interface moves inward, the inner oxide structures suffer deeper oxidation and transform into the globular oxide structures. Our results demonstrate that the unique oxidation characteristics and the understanding of formation mechanisms pave the way for the exploration and development of advanced oxidation-resistant TiAl-based materials.