Abstract:The corrosion behavior of ternary Fe-15Cu-5Al (mole fraction, %) alloy was studied at 1 000 ℃ in 0.1 MPa pure oxygen. The Fe-rich alloy shows two parabolic oxidation stages, with a small increase of the parabolic rate constant from 1.9×10⁻⁹ to 4.1×10⁻⁹ g²/(cm⁴∙s). The scale grown on the alloy is very complicated, with formation of overgrown nodules interspersed among bulky stratified scales. The nodules and the bulky stratified scales are always composed of an outer layer of CuFe₂O₄ and of an inner layer containing Fe₂O₃ and Fe₃O₄. Beneath the external scale of the nodules, there is an internal oxidation zone where iron oxide is mixed with copper metal. Furthermore, the base of the internal oxidation zone is characterized by a discontinuous aluminum-enriched layer of either Al₂O₃ or FeAl₂O₄. For the stratified scales, no internal oxidation zone is present beneath the innermost Al₂O₃ or FeAl₂O₄ layer. Aluminum depletion is present in advance of the internal oxidation front, while iron depletion is not observed. The corrosion feature of the ternary Fe-15Cu-5Al alloy is partly associated with that of the corresponding binary Fe-Cu and Fe-Al alloys. The peculiar scale microstructure observed is considered mainly as a consequence of the limited solubility of the iron and copper components in one another and of the monovariant system of the ternary Fe-15Cu-5Al alloy.

Key words: Fe-15Cu-5Al alloy; ternary alloy; corrosion behavior; nodules