Phase Equilibria and Thermodynamic Properties in the Fe-Cr System

Xiong, Wei; Selleby, Malin; Chen, Qing; Odqvist, Joakim; Du, Yong

doi:10.1080/10408431003788472

Cited by 187 publications

(120 citation statements)

References 158 publications

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“…% Cr) 2 . Their excellent properties make them candidate materials for future fusion nuclear reactors 3,4 , one of the reasons that induced a considerable amount of work on the various aspects of the Fe-Cr alloy both experimentally 5,6 and theoretically 7 .…”

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confidence: 99%

Anomalous surface segregation profiles in ferritic Fe-Cr stainless steel

Levesque

2013

Phys. Rev. B

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The iron-chromium alloy and its derivatives are widely used for their remarkable resistance to corrosion, which only occurs in a narrow concentration range around 9 to 13 atomic percent chromium. Although known to be due to chromium enrichment of a few atoms thick layer at the surfaces, the understanding of its complex atomistic origin has been a remaining challenge. We report an investigation of the thermodynamics of such surfaces at the atomic scale by means of Monte Carlo simulations. We use a Hamiltonian which provides a parameterization of previous ab initio results and successfully describes the alloy's unusual thermodynamics. We report a strong enrichment in Cr of the surfaces for low bulk concentrations, with a narrow optimum around 12 atomic percent chromium, beyond which the surface composition decreases drastically. This behavior is explained by a synergy between (i) the complex phase separation in the bulk alloy, (ii) local phase transitions that tune the layers closest to the surface to an iron-rich state and inhibit the bulk phase separation in this region, and (iii) its compensation by a strong and non-linear enrichment in Cr of the next few layers. Implications with respect to the design of prospective nanomaterials are briefly discussed.PACS numbers: 64.75. Nx, 68.35.bd, 61.66.Dk, 64.70.kd, 81.30.Bx The iron-chromium alloy and its derivatives are inexpensive, have satisfactory mechanical properties and above all exhibit a remarkable resistance to corrosion: it is the most widely used class of alloy in the world. Its outstanding corrosion resistance is known for a century 1 to only occur in a narrow range of concentrations, around 10 atomic percent of chromium (at. % Cr) 2 . Their excellent properties make them candidate materials for future fusion nuclear reactors 3,4 , one of the reasons that induced a considerable amount of work on the various aspects of the Fe-Cr alloy both experimentally 5,6 and theoretically 7 .Corrosion resistance of stainless steels is due to the passivation of the material by an inert, chromium rich layer at the interface between the alloy and the environment, i.e. at the surfaces. Passivation is a phenomena inherent to how much Cr is located at the surfaces, which is a non-linear function of the bulk concentration 8 . In austenitic Fe-Cr, which only exists at high temperatures above ≈ 800 C and for less than ≈ 10 at. % Cr, the more chromium in the bulk, the more chromium in the surface and thus the more stainless the alloy. In ferritic Fe-Cr alloys, the picture is more complex. Without additive elements, the Cr content at which the alloy is passivated is narrow, from 9 to 13 at. % Cr, beyond which occurs an increase in the corrosion rate and a strong decrease in mechanical properties.This important property of stainless steels has been extensively studied, but its complex origin at the atomic scale has remained a missing understanding, subject to controversial findings: How chromium causes passivation, i.e. how it interacts and reacts with chemical elements coming fr...

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confidence: 99%

Anomalous surface segregation profiles in ferritic Fe-Cr stainless steel

Levesque

2013

Phys. Rev. B

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“…Cr, the BCC Fe-Cr solid solution alpha phase coexists with a lower symmetry, slightly Fe-rich sigma phase above this eutectoid boundary up to the vicinity of 600 -650°C where the system becomes totally miscible 23 .…”

Section: Materials Propertiesmentioning

confidence: 99%

“…4). The boundary of the miscibility gap where the binary alloy Fe22%Cr separates into Fe-and Cr-rich alpha phases is located between 500 -510°C 23 . At 22%…”

Section: Materials Propertiesmentioning

confidence: 99%

Characterization of the interface between an Fe–Cr alloy and the p-type thermoelectric oxide Ca3Co4O9

Holgate

Han

et al. 2014

Journal of Alloys and Compounds

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of the interface between an Fe-Cr alloy and the p-type thermoelectric oxide Ca 3 Co 4 O 9 , (2013), doi: http://dx.doi.org/10. 1016/j.jallcom.2013.08.096 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Characterization of the interface between an AbstractA customized Fe-Cr alloy that has been optimized for high temperature applications in oxidizing atmospheres has been interfaced via spark plasma sintering (SPS) with a p-type thermoelectric oxide material: calcium cobaltate (Ca 3 Co 4 O 9 ). The properties of the alloy have been analyzed for its compatibility with the Ca 3 Co 4 O 9 in terms of its thermal expansion and transport properties. The thermal and electrical contact resistances have been measured as a function of temperature, and the long term electronic integrity of the interface analyzed by measuring the resistance versus time at an elevated temperature. The kinetics of the interface have been analyzed through imaging with scanning electron microscopy (SEM), elemental analysis using energy dispersive spectroscopy (EDS), and phase identification with X-ray diffraction (XRD). The results reveal the formation of an intermediate phase containing calcium and chromium in the interface that is highly resistive at room temperature, but conducting at the intended thermoelectric device hot-side operating temperature of 800°C. As the alloy is well matched in terms of its thermal expansion and highly conducting compared to the Ca 3 Co 4 O 9 , it may be further considered as an interconnect material candidate at least with application on the hot-side of an oxide thermoelectric power generation module.

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“…62,63 Therefore, Fe-Cr alloy is a good model alloy to demonstrate the capability of the phase-field modeling. Next we present a generic phase-field model describing multiple microstructure evolution phenomena in irradiated Fe-Cr alloys.…”

Section: Part Ii: Thermodynamic and Kinetic Models Of Irradiated Fe-cmentioning

confidence: 99%