Oxidation of 1 and 5 weight percent aluminum-iron base alloys has been investigated in oxygen at one atmosphere pressure over the temperature range 500-1000 C (932-1832 F). Effects of temperature and alloy composition on oxidation rate were determined by a gravimetric method. Oxide scales formed on alloy surfaces were examined by metallography, electron diffraction and electron microprobe analysis.
During the initial period of reaction the oxidation process obeyed a parabolic rate law. After prolonged exposure oxidation occurred at a constant rate. Several layers consisting of oxide mixtures were observed on oxidized specimens. The innermost layer was found to have a high aluminum content, whereas the outermost layer was found to be mainly iron oxide.
