A combined electron microscopy, atom probe tomography and small angle X-ray scattering study of oxide dispersion strengthened 18Cr ferritic steel

摘要

Dispersion of nano Y2O3 (0.35 wt.%) in 18Cr ferritic steel (Fe-18Cr-2.33W-0.34Ti) was achieved by high energy ball milling of pre-alloyed powders after 6 h. The severe deformation induced nano-structuring during ball milling led to metastable solid solution formation, which gets stabilized during consolidation by upset forging and hot extrusion. Transmission electron microscopy, atom probe tomography and small angle X-ray scattering were combined to comprehensively characterize the crystal structure, morphology and the chemical composition of the dispersoids. Accordingly, the dispersoids of the type Y2Ti2O7 with cuboidal shape and Fd (3) over barm diamond cubic crystal structure having a lattice parameter of 1.01 nm were observed. The plastic deformation behavior of ODS steels at different operating temperatures was studied using the tensile test and the results were correlated with the size and morphology of the dispersoids.