Abstract
A 9Cr-ODS steel was prepared by mechanical alloying and hot isostatic pressing methods. The microstructures were characterized by high-resolution transmission electron microscopy and high-angle annular dark field scanning transmission electron microscopy( HAADFSTEM). Helium ions of 4 × 1017/cm2 were respectively implanted into the 9Cr-ODS steel and non-ODS Eurofer97 steel with a 400 keV ion accelerator,and the sizes of helium bubbles in the two steels were observed by HAADF-STEM. The results show that the average grain size of the9Cr-ODS steel is about 0. 5 μm. Two kinds of precipitates were observed in the ODS steel: highdensity nano-size Y2Ti2O7 and large Mn( Ti) Cr2O4 formed mainly at the grain boundaries. The size of the helium bubbles in ODS steels is much more smaller than that in Eurofer97 steel,which means that the nano-size precipitates are helpful to suppress the formation of coarse helium bubbles.
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