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Effect of Fe and partial pressure of oxygen on the formation and phase transformation behavior of Al 2 O 3 scale
Author(s) -
Hayashi S.,
Takada Y.,
Saeki I.,
Yamauchi A.,
Nishiyama Y.,
Doi T.,
Kyo S.,
Sato M.
Publication year - 2012
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201206731
Subject(s) - metastability , alloy , partial pressure , materials science , phase (matter) , lattice (music) , oxygen , analytical chemistry (journal) , crystallography , metallurgy , chemistry , physics , organic chemistry , chromatography , acoustics
The effect of oxygen partial pressure on the phase transformation of Al 2 O 3 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 Al 2 O 3 formation, but little effect was observed when the samples were oxidized in a low partial pressure of oxygen. Under the low ${\rm P}_{{\rm O}_{{\rm 2}} } $ atmosphere, metastable to stable α‐Al 2 O 3 scale phase transformation on both Fe‐coated and non‐coated Fe–Al alloys was significantly delayed. The lattice spacing of α‐Al 2 O 3 scale formed in air decreased with increasing alloy Al content. Further decrease in the lattice spacing of α‐Al 2 O 3 scale was observed when the alloy was oxidized in low ${\rm P}_{{\rm O}_{{\rm 2}} } $ . The results obtained clearly indicated that the formation of Fe 2 O 3 or Fe 3+ in metastable Al 2 O 3 accelerated the metastable to stable α‐Al 2 O 3 scale transformation.