Nanoscale characterization of ODS Fe–9%Cr model alloys compacted by spark plasma sintering

Ferritic/martensitic high-chromium steels are leading candidates for fission and fusion reactor components. Oxide dispersion strengthening is an effective way to improve properties related to thermal and irradiation-induced creep and to extend their elevated temperature applications. An extensive experimental study focusing on the microstructural characterization of oxide-dispersion strengthened Fe–9wt%Cr model alloys is reported. Several material variants were produced by means of high-energy milling of elemental powders of Fe, Cr and commercial yttria powders. Consolidation was based on spark plasma sintering. Special emphasis is placed on the characterization of the nano-particles using transmission electron microscopy, small-angle neutron scattering and atom probe tomography. The microstructure of the investigated alloys and the role of the process parameters are discussed. Implications for the reliability of the applied characterization techniques are also highlighted.

► Spark plasma sintered Fe9Cr–xY2O3 (x = 0, 0.3, 0.6) characterized by SANS and TEM.
► A consistent description of the microstructure was achieved.
► Y-free and Y-O-rich nano-particles found, radius 2–15 nm, Y:O ratio 1:2–1:3.
► Both types are stable during additional HIP treatment in Y2O3-containing alloys.
► Growth of Y-free particles observed during HIP treatment of Y2O3-free reference.