Oxide dispersion strengthened (ODS) steels offer superior strength and creep resistance at high temperatures due to the reinforcement of fine nanosized oxides dispersed throughout the matrix. These alloys have been applied in the aerospace, thermal processing and glass processing industries. Due to their exceptional strength and creep resistance at high temperatures, they became one of the most promising candidates for material components in the nuclear power plants. The addition of Ti to these alloys reduces the particle size, leading to higher dispersion of fine Y-Ti-oxide particles. These oxides block mobile dislocations, resulting in increased hardness and strength. The most common types of such oxides which were reported to exist in these steels are Y2Ti2O7 and Y2TiO5. However, most common diffraction patterns shown in the literature for these structures can also be indexed in terms of Y2O3, and despite numerous studies focused on the characterization of these oxides, ambiguity regarding their composition and structures remains. Since structure and properties of materials are intimately linked, in depth characterization is crucial for understanding of physical properties. In the present study, detailed transmission electron microscopy (TEM) analysis, including high angular annular dark field (HAADF) and energy filtered TEM (EFTEM), was conducted in order to determine the distribution, composition and structure of oxide particles in a 14wt% Cr ODS alloy. It was found that oxides are composed mainly of Y, Ti and O. However, diffraction patterns obtained from several particles could not been indexed in terms of the Y2Ti2O7 or Y2TiO5 structures. Electron diffraction tomography data set obtained from one particle was successfully indexed in terms of YTiO3 (distorted perovskite derivative), which is rarely reported in the literature regarding these steels.
