OXYGEN-UPTAKE AND DEPLETION LAYER FORMATION DURING OXIDATION OF GAMMA-TIAL BASED ALLOYS

The oxidation behaviour of gamma-TiAl based intermetallics has been in vestigated at 900 degrees C in an oxygen-argon mixture. During oxidati on a depleted layer is formed at the scale/alloy interface. This deple ted layer can be single- or two-phase. Using X-ray diffraction, electr on probe microanalyses and optical microscopy studies the two Ti-Al-O phases which can form in the depletion layer were identified as Z-phas e (Ti5Al3O2) and an interstitial solid solution of alpha(2)-Ti3Al(O). Apart from this depletion layer, a further oxidation affected zone was found beneath the oxide scale. This zone is much wider than the deple ted layer and is believed to be formed by Al-depletion and oxygen upta ke in the gamma-TiAl grains. The width of the zone depends on alloy co mposition and microstructure. (C) 1997 Elsevier Science Ltd.