Evaluation of microstructural parameters of oxide dispersion strengthened steels from X-ray diffraction profiles

The microstructural parameters of oxide dispersion strengthened (ODS) steels from measured diffraction profiles were evaluated using an approach where the complex oxide nanoparticles (Y₂Ti₂O₇ and Y₄Al₂O₉) are modeled as spherical inclusions in the steel matrix with coherent or incoherent boundaries. The proposed method enables processing of diffraction data from materials containing spherical inclusions in addition to straight dislocations, and taking into account broadening due to crystallite size and instrumental effects. The parameters of crystallite size distribution modeled by a lognormal distribution function (the parameters m and σ), the strain anisotropy parameter q, the dislocation density ρ, the dislocation arrangement parameter M, the density of oxide nanoparticles ρ_np and the nanoparticle radius r₀ were determined for the ODS steel samples. The results obtained are in good agreement with the results of transmission electron microscopy (TEM).