Oxide dispersion strengthened (ODS) steels have been considered as candidate structural material for nuclear power systems, such as cladding material of Gen. IV fission reactors and first wall structural material for fusion DEMO reactors. It has excellent creep strength and neutron irradiation tolerance. Also, high-Cr ODS steels added with Al have good corrosion resistance, although Al is not adequate for the application to fusion system because of high radioactivation. In this study, the recrystallization behavior is investigated by means of hardness measurement and grain morphology observation for two types of ODS steels, which are Al-added (Fe-15Cr-2W-3Al-0.5Zr-0.3Y_2O_3) and Al-free (Fe-15Cr-2W-0.2Ti-0.3Y_2O_3) ODS steels. The results of hardness measurement and EBSD analysis indicated that the Al-added ODS steel recrystallized at lower temperatures, and coarser grain growth occurred than the Al-free ODS steel. The strength of Al-added ODS steel was lower than that of Al-free ODS steel, and no marked isotropy was observed at room temperature. The tensile specimens with longitudinal direction showed high strength and some isotropy at 700°C. Since Al-free ODS steel consists of finer oxide particles than Al-added ODS steel, it is considered that the retardation of recrystallization in the Al-free ODS steel is due to fine oxide particles which pin down the grain boundaries more effectively than those in Al-added ODS steel.
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