(S)TEM study of different stages of Ti–45Al–8Nb–0.2W–0.2B–0.02Y alloy oxidation at 900 °C

The oxidation process of Ti–45Al–8Nb–0.2W–0.2B–0.02Y (at%) can be divided into three stages during 100 h at 900 °C. The change of ion diffusion path leads to the discontinuity of the oxidation curve between the second and third stage. Different stages of oxidation morphology have been investigated combined with TEM and STEM. AlNb2 phase forms at the interface of oxide scale/base alloy. Contrary to a continuous formation of ‘x’ phase in γ-TiAl with Nb free at the interface of oxide scale/base alloy. AlNb2 phase hinder continuous ‘x’ phase formation, which can promote TiAl oxidation protection.