Etude de l’élaboration d’aciers renforcés par dispersion d’oxydes par procédé alternatif de mécanosynthèse

Abstract : This study concerns the development of an innovative manufacturing process for oxidedispersion strengthened steel (hereafter referred to as “ODS”) by mechanosynthesis. As part of materials development for Sodium-cooled Fast Reactors (SFR), the aim is to prevent the growth of undesirable micrometric precipitates which can drastically degrade steel’s mechanical properties. This new process introduces Y2Ti2O7 pyrochlore oxide nanoparticles directly into Fe-Cr metallic powder through mechanical milling. To achieve this, a process has been set up to synthesize Y2Ti2O7 pyrochlore oxides via mechanical alloying of nanosized Y2O3 and TiO2 powders. Optimization of the milling parameters enabled the production of a pure nanostructured powder of the desired nature. Thereafter, the innovative ODS steel manufacturing process was validated on a small and then semiindustrial scale. This new process was used to study the impact of milling parameters and chemical composition on the produced material’s features and enabled the establishment of a link between milling conditions, microstructure and mechanical properties. This study first enables the validation of the method of introducing precipitates in the form of Y2Ti2O7 oxides as an efficient way to obtain competitive ODS steel. Moreover, it reveals the importance of the features of the manufacturing process, particularly milling conditions, on the microstructure and mechanical properties of ODS steel. The results reveal promising perspectives concerning the features of ODS steel manufacturing.
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Esther Simondon. Etude de l’élaboration d’aciers renforcés par dispersion d’oxydes par procédé alternatif de mécanosynthèse. Matériaux. INSA de Rennes, 2018. Français. ⟨NNT : 2018ISAR0023⟩. ⟨tel-02135245v2⟩

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