Oxide dispersion strengthened (ODS) steels exhibit superior mechanical properties and irradiation resistance due to nano-sized oxides, highly dispersed in the metallic matrix. The mechanical properties are affected by the structure, composition, size and density of the nano-sized oxides. Despite numerous reports on the characterization of these oxides, ambiguity regarding their composition, crystallographic structure and orientation relationship with the matrix remains. In the present study, characterization of the crystallographic structure of oxide particles existing in 14%Cr ODS steel was performed using classical and novel transmission electron microscopy (TEM) methods. 3D dispersion, density and composition of these oxides were evaluated by atom probe tomography (APT). Three populations of particles were detected: highly dispersed, 3–20 nm Fe(Cr,Ti,Y)O particles with spinel structure; 50–150 nm YTiO3 and large (100–200 nm) particles identified as cubic TiC. The spinel-type particles displayed Bain and Kurdjumov-Sachs orientation relationships (OR) with the ferritic matrix. Applying electron diffraction tomography, the YTiO3 structure was attributed to the GdFeO3 (distorted perovskite)-type and its lattice parameters were refined as a = 5.46 A, b = 7.66 A and c = 5.28 A. Orientation relationship of the YTiO3 particles and Fe matrix were determined as [110]Fe//[210]oxide and (110)Fe//(002)oxide.
