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Etude par Sonde Atomique Tomographique de la formation de nano-particules dans les aciers ODS et NDS

Abstract : FeCr ferritic or martensitic matrix reinforced by a thin and dense oxide dispersion (ODS steels) exhibit good radiation resistance and mechanical properties at high temperature. Thus, ODS steels are considered as candidate materials for core elements of future nuclear reactors. Based on this positive experience, a new type of material, inside which the oxide dispersion is replaced by a nitride dispersion (NDS steels) was elaborated at CEA Saclay. Two distinct ways of elaboration were used: mechanical alloying (MA) and nitriding. In this work, ODS and NDS steels were investigated at different steps of elaboration process (as-milled/as-nitrided, annealed up to 1000ºC and consolidated states) by Atom Probe Tomography and others complementary techniques. In ODS steels, it was shown that two simultaneous mechanisms occur during MA: dissolution of initial yttria powder and formation of Y-O-rich clusters due to precipitation and/or resulting from an incomplete dissolution. During subsequent annealing and consolidation, Y-O-rich clusters act as nuclei for formation of Y-Ti-O-rich nanoparticles. As far as NDS steels are concerned, it was shown that MA is an effective elaboration process. The microstructure contains significant amount of nanometer scale nitrides. An important feature is that their nucleation starts during MA process. As for the consolidated material, nanometer sizes and high number densities of nitrides are comparable to the values measured in different ODS steels. Concerning nitriding process, different types of nitrides (CrN, TiN) were observed in the NDS steels. However, the investigations showed that the microstructure is largely heterogeneous in this case and further optimization of the process are required for further application.
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Submitted on : Wednesday, November 14, 2012 - 12:02:23 PM
Last modification on : Thursday, May 16, 2019 - 1:18:02 PM
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  • HAL Id : tel-00751814, version 1

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Olena Kalokhtina. Etude par Sonde Atomique Tomographique de la formation de nano-particules dans les aciers ODS et NDS. Science des matériaux [cond-mat.mtrl-sci]. Université de Rouen, 2012. Français. ⟨tel-00751814⟩

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