Selective Oxide Films of a 5% Aluminum-Iron Alloy in a Low Oxygen Potential Atmosphere

Abstract

Selective oxide films on a 5% Al-Fe alloy in the temperature range 700–900 C (1292–1652 F) for 1 hour in an atmosphere of hydrogen-water vapor mixture with a constant dewpoint as low as 20 C (68 F) were identical with the spinel type crystals, γ-Al₂O₃, containing small amounts of iron. Oxide films however, produced after heating at higher temperatures than 920 C (1688 F) in the same oxidizing atmosphere consisted only of corundum type crystals, α-Al₂O₃, having iron. It is probable that the iron ions contribute to the formation of the corundum type oxide at the temperature of the stable region of pure γ-Al₂O₃.