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Oxide dispersion–strengthened (ODS) FeCrAl alloys are an advanced cladding material that combines the high-temperature steam oxidation resistance of conventional wrought FeCrAl with the irradiation resistance and high-temperature strength of nanostructured ferritic alloys. In the present study, the effect of microstructure on the performance of the ODS FeCrAl alloy system in light-water reactor–accident scenarios is evaluated using a combination of experimentation and modeling. ODS FeCrAl alloy with nominal composition Fe-12Cr-6Al-0.3Zr-0.3Y2O3 was produced into a thin-walled tube via high-precision tube rolling. A portion of the as-received (AR) tube was subjected to a full recrystallization heat treatment. Both variants were subjected to burst testing at Oak Ridge National Laboratory’s Severe Accident Test Station. The recrystallized tube exhibited burst temperature margins 200 °C higher than that of C26M, whereas the AR tube only achieved burst properties comparable to the wrought FeCrAl alloy. The burst experiments were simulated in the BISON finite element code through the development of new viscoplastic material databases for each heat treatment condition, informed by high temperature tensile tests of tube specimens and existing literature data on creep mechanisms. Finally, an ODS FeCrAl burst criterion was obtained using simulated burst experiments across the entire range of test conditions.

To develop advanced nuclear fuel claddings, two oxide dispersion strengthened (ODS) alloys were designed, manufactured, and evaluated. First, 12 %Cr alloy, is an ODS-version of ferritic steel, and second, 10 %Cr-6 %Al alloy, is a high-strength version of accident tolerant iron-chrome-aluminum alloy. Their properties and performance were compared with “classical” ODS material, 14 %Cr alloy 14WYT. Thin-walled (∼500 µm wall thickness) tubes were manufactured successfully using the pilgering technique. For all alloys, axial tensile specimens exhibited high tensile strength (>1 GPa) and reasonable plastic strains (10–17%). Ring tensile specimens, conversely, showed limited ductility (∼1%) with similar strengths to those measured in the axial orientation. The grain size, precipitate dispersion characteristics, and dislocation densities were then used to estimate yield strengths that were compared against room temperature axial and ring-pull tensile test data. The strengthening models showed mixed agreement with experimentally measured values due to the highly anisotropic microstructures of all three ODS tubes. These results illustrate the need for future model optimization to accommodate non-isotropic microstructures associated with components processed using rolling/pilgering approaches. In all cases, atom probe tomography and energy-filtered transmission electron microscopy demonstrated that ODS structure survived multiple pilgering operations, and precipitate microstructure evolution matched well the state-of-the-art nanoprecipitate coarsening models.

Additive manufacturing processes supplement traditional material processing routes with unique capabilities which can have profound impacts on component production. Physical prototyping is accelerated and the fabrication of complex components, difficult or impossible to produce conventionally, is realized. Metals research is often focused on identifying process windows to avoid defects which thereby yield desirable properties. In electron beam melting fusion processes, however, precise spatial control of the heat source allows for detailed microstructure manipulation. Design is therefore extended to the microstructure scale offering greater overall flexibility towards engineering high performance components. In this work the role of geometry and beam path sequencing in a powder bed electron beam melting process is investigated. It is observed that by carefully engineering the melting sequence the morphology and texture at the mesoscale can be controlled. Solidification in the build direction, which usually prefers [001] directions, is tilted by control of the heat flux vector which yields large columnar crystals with a strong [011] build direction preference. This newly developed conduction control strategy is demonstrated for producing alternating mesoscale structures in bulk samples. Furthermore, a new scanning strategy is demonstrated which may be suitable for promoting a randomized crystallographic texture during the additive manufacturing process.