Microstructural characterization and strengthening mechanisms of a 12Cr-ODS steel

The microstructure of the 12Cr-ODS steel was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD) techniques. The results showed that the microstructure consisted of fine and elongated grains, high density of dislocations, and large concentration of nm-scale oxide particles, which were identified as five types of crystal structures by high resolution TEM (HRTEM) imaging, such as monoclinic and cubic Y₂O₃, hexagonal and orthorhombic Y₂TiO₅, and cubic Y₂Ti₂O₇. The dominant {001}<110> component and weaker <111> parallel to normal direction texture were observed. Besides, the yield stress was experimentally measured and quantitatively estimated. The findings indicated that theoretical calculation was in accordance with the experimental measurements, and strengthening contributions from solid-solution atoms and grain boundaries were linearly additive, whereas those from dislocations and oxide dispersoids were averaged by root mean square summation.