Classical Many-Body Potential for Concentrated Alloys and the Inversion of Order in Iron-Chromium Alloys

Caro, A.; Crowson, D. A.; Caro, M.

doi:10.1103/physrevlett.95.075702

Cited by 145 publications

(124 citation statements)

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“…Influenced by the strategy of Caro et al 25 , the order energy is advantageously expressed as a simple concentration and temperature dependent RedlichKister 30 expansion:…”

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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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“…Influenced by the strategy of Caro et al 25 , the order energy is advantageously expressed as a simple concentration and temperature dependent RedlichKister 30 expansion:…”

mentioning

confidence: 99%

Anomalous surface segregation profiles in ferritic Fe-Cr stainless steel

Levesque

2013

Phys. Rev. B

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“…14, that reproduces static and dynamic properties quite satisfactorily. 15 The free energy calculations are then performed using a thermodynamic package that we developed for this purpose, and is reported in detail in Refs. [16][17][18][19][20].…”

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Implications of ab initio energetics on the thermodynamics of Fe–Cr alloys

Caro

Lopasso

et al. 2006

Applied Physics Letters

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“…Les alliages Fe-Cr de concentrations voisines de la concentration d'inversion présentent des applications potentielles pour les cuves des nouveaux réacteurs nucléaires ainsi que pour la fusion (projet ITER), car ils sont susceptibles de résister à de hautes températures et de fortes irradiations sans ségréger. L'étude de l'ordre local dans Fe-Cr suscite donc actuellement de nombreux travaux [14,15].…”

Section: Inversion De L'ordre Local Dans Les Alliages De Fer-chromeunclassified

Ordre local

Mirebeau¹

2008

Études Structurales Par Diffraction Des Neutrons

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Résumé. L'ordre local entre atomes ou moments magnétiques joue un rôle important en physique de la matiére condensée. La diffraction de neutrons constitue un outil de choix pour son étude microscopique. Ce chapître présente quelques cas simples, dans les solutions solides d'alliages binaires, d'ordres chimiques ou magnétiques locaux qui peuvent être facilement modélisés et fournir des informations quantifiables. Il présente aussi un bref aperçu de phénomènes dont l'ordre local est précurseur, comme la séparation de phase ou la transition vers un ordre à longue distance. Enfin il donne des exemples des composés géométriquement frustrés, où des ordres magnétiques locaux originaux, liquide de spin, glace de spin ou verre de spin chimiquement ordonné, sont stabilisés, et dans lequel l'état magnétique fondamental évolue sous pression.

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Classical Many-Body Potential for Concentrated Alloys and the Inversion of Order in Iron-Chromium Alloys

Cited by 145 publications

References 10 publications

Anomalous surface segregation profiles in ferritic Fe-Cr stainless steel

Anomalous surface segregation profiles in ferritic Fe-Cr stainless steel

Implications of ab initio energetics on the thermodynamics of Fe–Cr alloys

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