Evaluation of fracture behavior of recrystallized and aged high-Cr ODS ferritic steels

The effect of aging on the ductile to brittle transition behavior of recrystallized high-Cr ODS ferritic steels were investigated using small-punch test technique. In order to reduce the anisotropy of microstructure in the as-received ODS steels, they were recrystallized after cold rolling. The ODS steel without Al hardly recrystallized at 1200 °C for 90 min, while the ODS steel with Al significantly recrystallized. Ductile-brittle transition curves were drawn for as received, recrystallized, and thermally aged (at 450 °C for 1440 h). Before aging, both materials had good impact properties with low ductile-brittle transition temperatures and high USEs. The ductile-brittle transition temperatures are not dependent of the grain size. The aging degraded their impact properties for ODS steel with Al. However, almost no degradation occurred for the ODS steel without Al. SEM observation showed an influence of the cold-rolling direction on the fracture behavior especially at low temperatures.