Characterization of surface oxide layers formed on FeAl alloys by annealing under different atmospheres

XPS and SIMS were used for characterizing the surface oxide layers formed on FeAl alloys during annealing under atmospheres with different partial pressures of oxygen, which were controlled by H 2 O/H 2 ratios in the gas. The XPS results showed that an aluminum oxide (Al 2 O 3 ) layer was formed on the surfaces of samples annealed at a high temperature under a low partial pressure of oxygen, while such a layer was not formed on the surfaces of samples annealed under a high partial pressure of oxygen. SIMS depth profiles showed that the surfaces of samples annealed at high temperatures under a low partial pressure of oxygen were covered with a thin Al 2 O 3 layer of approximately 50 nm thickness. It was also shown that oxygen penetrated the samples annealed under a high partial pressure of oxygen, and the depth profile of oxygen was correlated with that of aluminum. This indicates that internal oxidation of aluminum occurs in the samples annealed under a high partial pressure of oxygen. Grazing‐incidence X‐ray diffraction (GIXD) was also employed for analyzing the structure of the Al 2 O 3 layer formed on the surface of samples annealed under a low partial pressure of oxygen. Copyright © 2008 John Wiley & Sons, Ltd.