The hardening of iron–chromium alloys under thermal ageing: An atomistic study

Bonny, G.; Terentyev, D.; Malerba, Lorenzo

doi:10.1016/j.jnucmat.2008.12.002

Cited by 33 publications

(12 citation statements)

References 34 publications

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“…In rigid lattice MC simulations [12,20,[34][35][36][37] using Ising-type interaction the Hamiltonian must be made temperature dependent. Semiempirical potentials have been used in both Metropolis MC (MMC) [38][39][40] and kinetic MC (KMC) [9,[41][42][43][44][45][46][47] studies. All works on kinetics are bulk simulations of single-crystal alloys and diffusion mediated by a single vacancy.…”

Section: B Large-scale Monte Carlo Simulationsmentioning

confidence: 99%

Segregation, precipitation, andα−α′phase separation in Fe-Cr alloys

et al. 2015

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Iron-chromium alloys, the base components of various stainless steel grades, have numerous technologically and scientifically interesting properties. However, these features are not yet sufficiently understood to allow their full exploitation in technological applications. In this work, we investigate segregation, precipitation, and phase separation in Fe-Cr systems analyzing the physical mechanisms behind the observed phenomena. To get a comprehensive picture of Fe-Cr alloys as a function of composition, temperature, and time the present investigation combines Monte Carlo simulations using semiempirical interatomic potential, first-principles total energy calculations, and experimental spectroscopy. In order to obtain a general picture of the relation of the atomic interactions and properties of Fe-Cr alloys in bulk, surface, and interface regions several complementary methods have to be used. Using the exact muffin-tin orbitals method with the coherent potential approximation (CPA-EMTO) the effective chemical potential as a function of Cr content (0-15 at. % Cr) is calculated for a surface, second atomic layer, and bulk. At ∼10 at. % Cr in the alloy the reversal of the driving force of a Cr atom to occupy either bulk or surface sites is obtained. The Cr-containing surfaces are expected when the Cr content exceeds ∼10 at. %. The second atomic layer forms about a 0.3 eV barrier for the migration of Cr atoms between the bulk and surface atomic layer. To get information on Fe-Cr in larger scales we use semiempirical methods. However, for Cr concentration regions less than 10 at. %, the ab initio (CPA-EMTO) result of the important role of the second atomic layer to the surface is not reproducible from the large-scale Monte Carlo molecular dynamics (MCMD) simulation. On the other hand, for the nominal concentration of Cr larger than 10 at. % the MCMD simulations show the precipitation of Cr into isolated pockets in bulk Fe-Cr and the existence of the upper limit of the solubility of Cr into Fe layers in Fe/Cr layer systems. For high Cr concentration alloys the performed spectroscopic measurements support the MCMD simulations. Hard x-ray photoelectron spectroscopy and Auger electron spectroscopy investigations were carried out to explore Cr segregation and precipitation in the Fe/Cr double layer and Fe 0.95 Cr 0.05 and Fe 0.85 Cr 0.15 alloys. Initial oxidation of Fe-Cr was investigated experimentally at 10 −8 Torr pressure of the spectrometers showing intense Cr 2 O 3 signal. Cr segregation and the formation of Cr-rich precipitates were traced by analyzing the experimental atomic concentrations and chemical shifts with respect to annealing time, Cr content, and kinetic energy of the exited electron.

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Section: B Large-scale Monte Carlo Simulationsmentioning

confidence: 99%

Segregation, precipitation, andα−α′phase separation in Fe-Cr alloys

et al. 2015

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“…Fe‐Cr alloys being representative of such steels are now being extensively investigated. For instance Bonny et al 34, 35 used AKMC techniques to study the phase separation processes during thermal annealing. They constructed the Fe‐rich phase boundary of the α – α ′ miscibility gap, compared it with the standard (CALPHAD) Fe–Cr and proposed a significant modification of the latter.…”

Section: Akmc Simulations Of Phase Transformations In Fe‐alloysmentioning

confidence: 99%

Introducing chemistry in atomistic kinetic Monte Carlo simulations of Fe alloys under irradiation

Becquart

Domain

2009

phys. stat. sol. (b)

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The evolution of alloy microstructures under non-equilibrium conditions such as irradiation is an important academic as wellindustrial issue. Atomistic kinetic Monte Carlo is one of the most versatile method which can be used to simulate the evolution of a complex microstructure at the atomic scale, dealing with elementary atomic mechanisms. It was developed more than 40 years ago to investigate diffusion events via the motion of a single vacancy, and the introduction of heterointerstitials or self-interstitials in the models is yet under development. This paper presents the key ingredients of the model, i.e. the algorithm, and some methods implemented to determine the cohesive energy as well as the activation energy. For purpose of simplicity and speed of calculations, most of the models developed so far apply to idealized lattices and model alloys, for example binary alloys. The extension of the models to more complex alloys is recent and an example of the simulation of multi-component Fe-CuNiMnSi alloys representative of pressure vessel steels is thus presented in more details. In particular, the adjustment procedures of the cohesive model are demonstrated as well as the validation of the model for vacancies and self-interstitials on thermal ageing and isochronal annealing experiments.

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“…Semiempirical potentials have been developed that take into account the change of sign of the mixing energy, such as the concentration-dependent model (CDM) of Caro et al 1 or the two-band model (2BM) of Olsson et al, 23 recently updated by Bonny et al 24 A lot of work has been done in order to assess their thermodynamic properties as well as their dynamical behavior. [25][26][27][28] However, it is still difficult to develop a potential that simultaneously fits all the key properties that control the thermodynamics and kinetics of the Fe-Cr decomposition (such as the mixing energies, the point defects formation energies, and migration barriers, with their dependence on the local atomic distribution and with the corresponding vibrational entropy contributions). Furthermore, magnetic contributions have not been introduced in these potentials.…”

Section: Introductionmentioning

confidence: 99%

Simple concentration-dependent pair interaction model for large-scale simulations of Fe-Cr alloys

Levesque

Martínez²,

Fu³

et al. 2011

Phys. Rev. B

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International audienceThis work is motivated by the need for large-scale simulations to extract physical information on the iron-chromium system that is a binary model alloy for ferritic steels used or proposed in many nuclear applications. From first-principles calculations and the experimental critical temperature we build a new energetic rigid lattice model based on pair interactions with concentration and temperature dependence. Density functional theory calculations in both norm-conserving and projector augmented-wave approaches have been performed. A thorough comparison of these two different ab initio techniques leads to a robust parametrization of the Fe-Cr Hamiltonian. Mean-field approximations and Monte Carlo calculations are then used to account for temperature effects. The predictions of the model are in agreement with the most recent phase diagram at all temperatures and compositions. The solubility of Cr in Fe below 700 K remains in the range of about 6 to 12%. It reproduces the transition between the ordering and demixing tendency and the spinodal decomposition limits are also in agreement with the values given in the literature

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The hardening of iron–chromium alloys under thermal ageing: An atomistic study

Cited by 33 publications

References 34 publications

Segregation, precipitation, andα−α′phase separation in Fe-Cr alloys

Segregation, precipitation, andα−α′phase separation in Fe-Cr alloys

Introducing chemistry in atomistic kinetic Monte Carlo simulations of Fe alloys under irradiation

Simple concentration-dependent pair interaction model for large-scale simulations of Fe-Cr alloys

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