TEM Observation of Loops Decorating Dislocations and Resulting Source Hardening of Neutron-Irradiated Fe-Cr Alloys

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Institutes & Expert groups

  • HZDR - Helmholtz,Zentrum Dresden, Rossendorf
  • CIEMAT - Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
  • CNRS - Centre national de la recherche scientifique

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Several open issues remain concerning the quantitative understanding of irradiation hardening in high-Cr steels. One of these issues is addressed here by correlating yield points that are observed in stress-strain curves with dislocation decoration observed by TEM for neutron-irradiated Fe-Cr alloys. It is found that both higher neutron exposure and higher Cr content promote irradiation-induced loops to arrange preferentially along dislocation lines. Consequently, the activation of dislocation sources requires unlocking from the decorating loops, thus resulting in a yield drop. This process is considered within the source hardening model as opposed to the dispersed barrier hardening model, the latter aimed to describe dislocation slip through a random array of obstacles. Microstructure-informed estimates of the unlocking stress are compared with measured values of the upper yield stress. As functions of neutron exposure, a cross-over from the dominance of dispersed-barrier hardening accompanied by smooth elastic-plastic transitions to the dominance of source hardening accompanied by yield drops is observed for Fe-9% Cr and Fe-12% Cr


Original languageEnglish
Article number147
Pages (from-to)1-10
Number of pages10
Issue number1
Publication statusPublished - 18 Jan 2020


  • Iron-chromium alloys, Neutron irradiation, Hardening, Tensile test, Dislocation loop, TEM

ID: 6772878