Small Scale Creep Testing of 14YWT via In-situ Transmission Electron Microscopy Irradiation and Nanoindentation

The next generation of nuclear materials must withstand severe operating conditions including high temperatures and irradiation exposure. Oxide dispersion strengthened steels, especially 14YWT, have shown promise as a durable material under these conditions. Understanding the irradiation-enhanced creep of structural components is fundamental to evaluating their suitability for applications in reactor environments. Ion irradiations can be used to expedite irradiation testing, but they have a restricted depth of penetration, limiting the characterization of changes to the material’s properties. Small-scale mechanical testing combined with ion beam irradiations has the potential to evaluate the irradiation-enhanced creep of materials. In this study, in-situ transmission electron microscopy nanopillar creep studies on 14YWT were performed with simultaneous ion beam irradiation. The irradiation increases the measured strain rate by an order of magnitude. Variable temperature ex-situ nanoindentation creep studies were performed between room temperature and 1073 K on control samples of 14YWT; observations indicated that there was a change in the deformation mechanism between 873 K and 1073 K, which agrees well with macro-scale mechanical testing. These results validate continued research into applying these meso-scale testing techniques to nuclear materials in the future.