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Fast three dimensional migration of He clusters in bcc Fe and Fe-Cr alloys
KTH, School of Engineering Sciences (SCI), Physics, Reactor Physics.
2009 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 105, no 10Article in journal (Refereed) Published
Abstract [en]

In this work, we perform atomistic molecular dynamics simulations to assess the properties of small helium vacancy (He-V) and pure He clusters in body-centered cubic Fe and in Fe-90-Cr-10 (Fe-10Cr) random alloy. The following two goals are pursued: determining diffusion mechanisms of He-V clusters occurring in dynamic simulations and revealing a possible influence of Cr on the mobility/stability of He-V clusters in the Fe-10Cr alloy. We also present a newly developed set of interatomic potentials for the Fe-Cr-He system, fitted to a set of specially performed density functional theory calculations. The obtained results show that the dissociation energies of the studied He-V clusters, as well as the migration energy of He interstitial, are not significantly affected in the alloy compared to pure Fe. It was found that small pure He clusters with sizes up to four atoms, that were assumed to be immobile in many previous studies devoted to He-release/accumulation kinetics, in fact, exhibit fast three dimensional motion with a migration energy of tens of meV. The presence of 10% Cr in the Fe matrix, however, retards their mobility. We discuss possible reasons for the decreased diffusivity of these He clusters in the Fe-Cr alloy.

Place, publisher, year, edition, pages
2009. Vol. 105, no 10
Keyword [en]
chromium alloys, density functional theory, diffusion, dissociation, energies, helium, iron, iron alloys, molecular dynamics method, potential energy functions, vacancies (crystal), helium-vacancy clusters, augmented-wave method, kinetic monte-carlo, interatomic potentials, alpha-iron, ferritic/martensitic steels, displacement cascades, thermal-stability, simulations, irradiation
URN: urn:nbn:se:kth:diva-18464DOI: 10.1063/1.3126709ISI: 000266500100078ScopusID: 2-s2.0-66549116073OAI: diva2:336511
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-01-24Bibliographically approved

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Sandberg, Nils
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