Innovative method of ODS steels manufacturing by direct introduction of pyrochlore phase through milling

This study concerns the development of an innovative manufacturing process for oxide-dispersion strengthened steels (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 FeCr metallic powder through mechanical milling, as compared to the standard Y2O3 + TiO2. This study enables the validation of the method of introducing precipitates in the form of Y2Ti2O7 oxides as an efficient way to obtain competitive ODS steels, with a more homogeneous microstructure, less coarse precipitates and more reliable impact properties compared to the conventional process. Moreover, it reveals the importance of the features of the manufacturing process, particularly of milling intensity and reinforcement rate, on the microstructure and mechanical properties of ODS steel. The results reveal promising perspectives concerning the features of ODS steel manufacturing. •ODS steels were produced by introducing Y2Ti2O7 nanoparticles directly into the FeCr powder through mechanical milling.•This lead to a more homogeneous microstructure and more reliable impact properties compared to standard ODS.•The influence of milling intensity and reinforcement rate on the material’s properties is also shown.•This study also shows the presence of « biphased » particles comprising two distinct orientations or structures.