Oxidation-induced microstructural changes of the TiAl TNM-B1 alloy after exposure at 900 °C in air

M.C. Galetz, A.S. Ulrich, C. Oskay, D. Fähsing, N. Laska, U. Schulz, M. Schütze

Intermetallics 123 (2020), 106830, DOI: 10.1016/j.intermet.2020.106830

This study focuses on the characterization of oxidation-induced microstructural changes in TNM®-B1 alloy due to the dissolution of oxygen during exposure at 900 °C for up to 1000h and investigates their correlation with the microstructural subsurface changes as well as their effect on the mechanical properties. For this purpose, the change in the phase distribution is measured during oxidation. In addition to measuring the embrittlement during exposure, the fracture strain and nanoindentation hardness of particular phases are assessed to reveal the impact of oxidation and of the resulting microstructural changes on their mechanical behavior. The subsurface embrittlement was found to be directly related to the oxygen content and to significant changes in the phase distribution of the oxygen-affected zone.

The transformation of βo-phase into α2 is proposed as an easily accessible indicator for oxygen uptake depth into the TNM alloy. Finally, the mechanism of embrittlement in the α2-phase is discussed.

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