Environmental embrittlement of a third generation γ TiAl alloy

Exposure of a Ti-45Al-5Nb alloy to elevated temperatures has been shown to result in a loss of ductility resulting from a near surface effect involving diffusion of oxygen into the alloy. Local electrode atom probe analysis was conducted at 2, 13, and 25 μm distance from the oxide/base-metal interface. Oxygen was preferentially located in the α2 phase with concentrations up to 14.8 at.% and diminishing with increasing distance from the surface. Near surface microstructural changes were only visible up to 10 μm from the surface but the oxygen diffusion significantly exceeded that distance. The diffusion coefficient of oxygen into the α2 phase was estimated based on the oxygen concentrations obtained from local electrode atom probe analysis. Fluorine ion implantation on the surface was investigated as a possible solution to the embrittlement.

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► LEAP analysis was utilized to study the diffusion of oxygen into a TiAl alloy.
► Oxygen diffusion exceeded the width of near surface microstructural changes.
► The diffusion coefficient of oxygen into α2 averaged 1.1 × 10−12 cm2/s at 800 °C.
► Flourine ion implantation does not prevent oxygen diffusion into the TiAl alloy.