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Abstract

The effect of oxygen partial pressure on the phase transformation of Al2O3 scale on various Fe–Al alloys with and without very thin (∼100 nm) Fe coating was investigated. Fe-coating on Fe–Al alloys can effectively suppress metastable Al2O3 formation, but little effect was observed when the samples were oxidized in a low partial pressure of oxygen. Under the low equation image atmosphere, metastable to stable α-Al2O3 scale phase transformation on both Fe-coated and non-coated Fe–Al alloys was significantly delayed. The lattice spacing of α-Al2O3 scale formed in air decreased with increasing alloy Al content. Further decrease in the lattice spacing of α-Al2O3 scale was observed when the alloy was oxidized in low equation image. The results obtained clearly indicated that the formation of Fe2O3 or Fe3+ in metastable Al2O3 accelerated the metastable to stable α-Al2O3 scale transformation.