Surface Oxidation of Fe-48 mol%Al Single Crystal under a High Vacuum

In order to investigate the effect of aging heat treatment and surface orientation on oxidation during the nanopore formation of B2-type FeAl, the surface of Fe-48 mol%Al single crystal was analyzed by Auger Electron Spectroscopy (AES). Electropolished and plasma-cleaned surfaces were aged for 18 ks at 723 K, in vacuum (about 5 × 10^-4 Pa). A thin oxide layer was already formed on the non-aged surface. A thicker oxide layer was grown on the aged surface, but the difference in thickness of the oxide layers was slight. Further, the orientation dependence of the thickness of the oxide layers was even smaller. The thickness of the oxide layer on the FeAl single crystal is comparable to that of the passive film on the aluminum foil. Therefore, it is concluded that the influence of the aging heat treatment on oxidation during the nanopore formation of B2-type FeAl is negligible.