Radiation induced phase instability of precipitates in reduced-activation ferritic/martensitic steels

Irradiation effects on precipitation were investigated in detail utilizing ion irradiation. F82H IEA heat, JLF-1 HFIR heat, aged F82H-IEA (873 K × 30 k h) and model alloy (Fe–Ta–C, aged) were used for experiments. The specimens were irradiated up to 10 or 20 dpa at 573 K or 773 K with 6.4 MeV Fe3+ ion or with degraded 1 MeV He+. It turned out that the size distribution of precipitates changed by ion irradiation just the same as it was observed in neutron irradiated RAFs, and precipitates in the ion irradiated region become amorphous. Laves phase in aged F82H was also amorphized. An aged Fe–Ta–C model alloy contained a high density of TaC in the matrix, but those TaC precipitates disappeared in the ion-irradiation region after 20 dpa single/dual ion irradiation. This amorphization of precipitates and TaC re-solution in these RAFs was also observed in neutron irradiated RAFs.