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Microchemical effects in irradiated Fe-Cr alloys as revealed by atomistic simulation

par Malerba, Lorenzo;Bonny, Giovanni;Terentyev, Dimitri ;Zhurkin, Eugeni;Hou, Marc ;Vörtler, Katharina;Nordlund, Kai
Référence Journal of nuclear materials, 442, 1-3, page (486-498)
Publication Publié, 2013

Article révisé par les pairs

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Résumé :

Neutron irradiation produces evolving nanostructural defects in materials, that affect their macroscopic properties. Defect production and evolution is expected to be influenced by the chemical composition of the material. In turn, the accumulation of defects in the material results in microchemical changes, which may induce further changes in macroscopic properties. In this work we review the results of recent atomic-level simulations conducted in Fe-Cr alloys, as model materials for high-Cr ferritic-martensitic steels, to address the following questions: 1. Is the primary damage produced in displacement cascades influenced by the Cr content? If so, how? 2. Does Cr change the stability of radiation-produced defects? 3. Is the diffusivity of cascade-produced defects changed by Cr content? 4. How do Cr atoms redistribute under irradiation inside the material under the action of thermodynamic driving forces and radiation-defect fluxes? It is found that the presence of Cr does not influence the type of damage created by displacement cascades, as compared to pure Fe, while cascades do contribute to redistributing Cr, in the same direction as thermodynamic driving forces. The presence of Cr does change the stability of point-defects: the effect is weak in the case of vacancies, stronger in the case of self-interstitials. In the latter case, Cr increases the stability of self-interstitial clusters, especially those so small to be invisible to the electron microscope. Cr reduces also significantly the diffusivity of self-interstitials and their clusters, in a way that depends in a non-monotonic way on Cr content, as well as on cluster size and temperature; however, the effect is negligible on the mobility of self-interstitial clusters large enough to become visible dislocation loops. Finally, Cr-rich precipitate formation is favoured in the tensile region of edge dislocations, while it appears not to be influenced by screw dislocations; prismatic dislocation loops (typically produced under irradiation) tend to be decorated by Cr. Cr has also tendency to accumulate at grain boundaries, while it tends to deplete in the proximity of free surfaces (at least in the absence of oxygen) and voids. © 2013 Elsevier B.V. All rights reserved.