Thermodynamics of the system iron-aluminum-oxygen between 1073 K and 1573 K

Elrefaie, F. A.; Smeltzer, W. W.

doi:10.1007/bf02654055

Cited by 7 publications

(9 citation statements)

References 17 publications

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“…8 together with experimental data [52,[54][55][56][57]. The experiments show consistency with regard to the liquidus on the Fe-rich side [54,55,57] and are well reproduced by the present model. The calculated melting of spinel is at 2058 K which can be compared to the reported melting temperatures of 2073 [66] and 2093 K [55,67].…”

Section: Resultssupporting

confidence: 80%

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Thermodynamic modeling of the aluminum–iron–oxygen system

Lindwall

Liu

Ross

et al. 2015

Calphad

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Section: Resultssupporting

confidence: 80%

“…The calculated vertical section along FeO-Al 2 O 3 is shown in Fig. 8 together with experimental data [52,[54][55][56][57]. The experiments show consistency with regard to the liquidus on the Fe-rich side [54,55,57] and are well reproduced by the present model.…”

Section: Resultssupporting

confidence: 75%

Thermodynamic modeling of the aluminum–iron–oxygen system

Lindwall

Liu

Ross

et al. 2015

Calphad

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“…8. The sequence of oxide phases is consistent with the observations from this investigation and with thermodynamic phase stability constraints of the Fe-AI-O system (12). The parabolic oxidation rate of these alloys when expressed in terms of the weight gain of oxygen per unit area, k~ ~ i0 -~ (kg O)2/m4-s, is three orders of magnitude less than the parabolic oxidation rate constant of pure iron, k2 = 2.5 • I0 -~ (kg O)-'/m4-s, (13) due to destabilization of the fast growing wustite (FeO) phase by a l u m i n u m as an alloying element in iron.…”

Section: Discussionsupporting

confidence: 91%

Oxidation Properties of Fe‐Al Alloys (1.5–5 a/o Al) in Oxygen at 1173 K

Mohamed

Smeltzer

1986

J. Electrochem. Soc.

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Oxidation properties of Fe-l.5, 3, and 5 atomic percent (a/o) A1 alloys were investigated at 1173 K in oxygen at 1 bar pressure. The reaction kinetics were represented by two limiting parabolic stages, a rapid initial stage and slow final stage separated by a transient period. The initial oxidation rate was more rapid with increasing alloy aluminum content. The reaction products of the 1.5 and 3 a/o A1 alloys formed a duplex scale consisting of an outer Fe~O:~ and an inner (Fe, A1):,O4 layers with FeAlzO,-A120:~ platelet precipitates which extended across the internal oxidation zone in the alloys. In the case of the Fe-5 a/o A1 alloy, a triplex Fe2OJ(Fe, A1):~OJAI~O:~ scale ultimately developed as the internal oxidation zone was completely converted to oxide upon growth of an AI~O~ film at the internal oxidation front.Oxidation resistance of steels is generally achieved by incorporating metallic elements which are selectively oxidized such as chromium and silicon to form adherent and slow growing oxide films. Aluminum is a prospective alloying element to protect iron from oxidation by forming a protective A120:~ film. Binary Fe-A1 alloys, nonetheless, have been the subject of only a few oxidation investigations (1-9); in consequence, the conditions and mechanisms for growth of various types of scales and internal precipitation of oxides are not yet understood. An attempt is made in this paper to more adequately define the mechanisms of scaling with concurrent internal oxidation and of the transition with increasing alloys aluminum content from internal oxidation to scale growth solely by examining the oxidation properties of iron alloys containing from 1.5 to 5 a/o Al. Experimental Alloys of nominal compositions 1.5, 3, and 5 atomic percent (a/o) A1 were prepared by electric arc melting of iron (99.95% pure) and aluminum (99.98% pure) containing impurity contents as published elsewhere (10) in an argon atmosphere gettered of oxygen by titanium chips. Actual compositions of these a-solid solution phase alloys were 1.56, 3.02, and 5.50 a/o A1. 3 and 5 a/o A1 were homogenized at 1473 K for 24h and the Fe-l.5 A1 alloy was homogenized at 1173 K for 170h in argon. Specimens 1.5 • 10-3m thick and of 0.01m diam were cut from these alloy ingots and subjected to metallographic polishing finishing with 1 ~m diamond paste.Oxidation runs were carried out in flowing oxygen (ultrapure grade) at 1 bar and 1173 K using a gravimetric assembly described previously (11). Oxide phases were identified by x-rays using Ni-filtered Cu-Ka radiation. Morphologies of reaction products were examined by light and electron (SEM) microscopy. Specimens were mounted in room setting epoxy resin, and, whenever etching was difficult, fracture cross sections were prepared. Energy dispersive x-ray analyses (EDAX) were used to determine distributions of elements in the various solid phases. Results

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“…This Al 2 O 3 , which has larger d-spacing, was reported on Fe-high Al binary alloys [10,11]. Cr 2 O 3 and Al 2 O 3 form a solid-solution [12], but solubility of Fe 2 O 3 in Al 2 O 3 is relatively small, 5.3 mol% at 1000°C [13], thus the d-spacing of initially formed a-Al 2 O 3 on higher Cr alloys could be larger than that formed on a lower Cr alloy.…”

Section: Discussionmentioning

confidence: 86%

The Transition from Transient Oxide to Protective Al2O3 Scale on Fe–Cr–Al Alloys During Heating to 1000 °C

2017

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The transition behavior of an Al-rich amorphous oxide layer to an external Al 2 O 3 layer on Fe-(4, 24)Cr-(6, 10)Al (at.%) alloys was investigated during heating to 1000°C at a heating rate of 50°C/min, by means of in situ hightemperature X-ray diffraction measurement and TEM observation. In the alloy containing 6Al, internal amorphous Al 2 O 3 was initially developed below the Al-rich amorphous surface layer. The amorphous internal precipitates transformed to be crystalline and grew laterally with time. The internal precipitates subsequently connected with each other to form a continuous a-Al 2 O 3 scale. In the case of 10Al alloy, an Al-rich amorphous layer transitioned to a crystalline a-Al 2 O 3 layer from the interface between transient/amorphous layers during heating. The Al 2 O 3 scale developed on high Al alloys contained Fe and Cr with relatively higher contents, but that formed on low Al alloy contained low Fe and Cr. The effect of Cr on promoting an external Al 2 O 3 scale formation was found to be weaker for alloys with higher Al content compared to the alloys with lower Al content, if Al 2 O 3 scale was directly transitioned from the amorphous layer.

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Thermodynamics of the system iron-aluminum-oxygen between 1073 K and 1573 K

Cited by 7 publications

References 17 publications

Thermodynamic modeling of the aluminum–iron–oxygen system

Thermodynamic modeling of the aluminum–iron–oxygen system

Oxidation Properties of Fe‐Al Alloys (1.5–5 a/o Al) in Oxygen at 1173 K

The Transition from Transient Oxide to Protective Al2O3 Scale on Fe–Cr–Al Alloys During Heating to 1000 °C

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