Pre- and post-deformation microstructures of oxide dispersion strengthened ferritic steels

Pre- and post-deformation microstructures and tensile properties of the newly-developed oxide dispersion strengthened (ODS) ferritic steels, K1 (Fe–19Cr–0.3W–0.3Ti–0.3Y2O3) and K4 (Fe–19Cr–4Al–2W–0.3Ti–0.3Y2O3) for nuclear fusion reactors and Generation IV nuclear fission systems were investigated. The nano-oxides of the K1 were cubic pyrochlore Y2Ti2O7, while those of K4 were mainly perovskite AlYO3, which was confirmed by transmission electron microscopy and X-ray diffraction (XRD) analyses. K1 was found to have much higher strength than K4 and the difference in the nano-oxides of K1 and K4 can account for this difference. Most of the extracted residues in the K1 and K4 identified by XRD consisted of M23C6 carbides.