Comprehensive Analysis of Nanostructure of Oxide Dispersion-Strengthened Steels by Ultramicroscopy Methods

The characterization of the nanostructure of modern oxide dispersion strengthened steels requires a comprehensive analysis using complementary techniques. In this work, the methods of small-angle X-ray scattering, transmission electron microscopy and atom probe tomography have been applied to several oxide dispersion strengthened steels. Comparison of the obtained results allows the most correct characterization of inclusion types and their number in the studied materials. It is shown that most of the studied steels contain oxide inclusions and nanosized clusters enriched in O and Y, as well as V, Ti, Al, and Zr, depending on the initial steel composition. Transmission electron microscopy and atom probe tomography provide detailed information about the inclusion types, and small-angle X-ray scattering gives the most accurate estimation of the average density of inclusions in large volumes of material. The importance of the correct determination of the inclusion types for hardening calculations is shown, the results of such calculations are compared with microhardness measurements. The calculated values of hardness for the studied steels are in the range 2.7–4.3 GPa, which is well confirmed by microhardness measurements.