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Effet du flux d’irradiation sur la formation de nano-défauts dans des alliages ferritiques Fe-Ni et Fe-Mn

Abstract : Reactor pressure vessel (RPV) steel embrittlement under neutron irradiation is the main lifetime limiting factor of nuclear reactors. This is due to the impeding of dislocation glide by nanometric clusters composed of Cu, P, Si, Mn and Ni. More specifically, radiation induced Mn and Ni enriched clusters cause a significant hardening at high dose. To predict this change in mechanical properties, particle accelerator based experiments are conducted. However, the achieved flux ranges between 10⁻⁴ and 10 ⁻ ⁶ dpa/s⁻ ¹, whereas it is limited to 10⁻ ¹ ⁰ dpa/s⁻ ¹ in modern nuclear power technologies. This point is of high importance since radiation damage highly depends on irradiation flux. The reproducibility ion-neutron is thus the key point. It has been studied in austenitic steels but little is known regarding any dose rate dependence in ferritic alloys. Therefore, this thesis focuses on the effect of ion fluxes on radiation damage in two different alloys : Fe-Ni and Fe-Mn in order to investigate, additionally, the effects of each solute on the microstructure after irradiation.The alloys were experimentally investigated using conventional Transmission Electron Microscopy, Scanning Transmission Electron Microscopy coupled to Energy Dispersive X-ray Spectroscopy and Electron Energy Loss Spectroscopy and by Atom Probe Tomography.Irradiations were performed with 2 MeV Fe³⁺ ions and 27 MeV Fe⁹⁺ ions at 400°C at a nominal damage rate of 10⁻⁴ and 10⁻ ⁶ dpa/s respectively, up to a nominal displacement damage of 1.2 dpa. The detailed analysis shows that Ni and Mn behave in a very different way in terms of nano-defects formed under irradiation.Besides, light particle irradiations were also performed in order to ascertain the cascade effects.Finally, a two-series irradiation was carried out using Fe ions at room temperature and protons at 400°C, to isolate the contribution of point defect clusters to hardening from that of solute enriched zones.
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https://tel.archives-ouvertes.fr/tel-02015365
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Submitted on : Tuesday, February 12, 2019 - 10:41:07 AM
Last modification on : Friday, October 23, 2020 - 5:04:34 PM
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  • HAL Id : tel-02015365, version 1

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Lisa Thinhinane Belkacemi. Effet du flux d’irradiation sur la formation de nano-défauts dans des alliages ferritiques Fe-Ni et Fe-Mn. Science des matériaux [cond-mat.mtrl-sci]. Université Paris-Saclay, 2018. Français. ⟨NNT : 2018SACLS441⟩. ⟨tel-02015365⟩

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