High resolution Transmission Electron Microscopy characterization of a milled oxide dispersion strengthened steel powder

M. Loyer-Prost (1) , J.S. Merot (2) , J. Ribis (1) , Y. Le Bouar (2) , L. Chaffron (1) , F. Legendre (1)

1 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
2 ONERA - The French Aerospace Lab [Châtillon]

Oxide Dispersion Strengthened (ODS) steels are promising materials for generation IV fuel claddings as their dense nano-oxide dispersion provides good creep and irradiation resistance. Even if they have been studied for years, the formation mechanism of these nano-oxides is still unclear. Here we report for the first time a High Resolution Transmission Electron Microscopy and Energy Filtered Transmission Electron Microscopy characterization of an ODS milled powder. It provides clear evidence of the presence of small crystalline nanoclusters (NCs) enriched in titanium directly after milling. Small NCs (<5 nm) have a crystalline structure and seem partly coherent with the matrix. They have an interplanar spacing close tothe (011) bcc iron structure. They coexist with larger crystalline spherical precipitates of 15e20 nm in size. Their crystalline structure may be metastable as they are not consistent with any Y-Ti-O or Ti-O structure. Such detailed observations in the as-milled grain powder confirm a mechanism of Y, Ti, O dissolution in the ferritic matrix followed by a NC precipitation during the mechanical alloying process of ODS materials.

Mots clés: MICROSCOPE ELECTRONIQUE; POUDRE METALLIQUE

Domaines: Matériaux

M. Loyer-Prost, J.S. Merot, J. Ribis, Y. Le Bouar, L. Chaffron, et al.. High resolution Transmission Electron Microscopy characterization of a milled oxide dispersion strengthened steel powder. Journal of Nuclear Materials, 2016, 479, p. 76-84. ⟨10.1016/j.jnucmat.2016.06.050⟩. ⟨hal-01403043⟩