Microstructural changes in Fe-10Cr-2Mo steel by neutron or charged particle irradiation

Abstract

An Fe-10Cr-2Mo type ferritic/martensitic dual phase steel. JFMS (Japanese ferrite/martensite steel), has been extensively studied in the Japanese fusion reactor materials research programs as a reference ferritic alloy. This work is intended to characterize the effects of neutron or charged particle irradiation to high doses on microstructural evolution and swelling of JFMS. Fast neutron irradiation was performed in an open packet in MOTA (materials open test assembly) during FFTF (fast flux test facility) cycle 10, at 643, 679, 793 and 873 K up to the maximum dose of about 40 dpa. For charged particle irradiation, 4 MeV nickel ions were injected up to 200 dpa, with or without helium ion implantation, at 723 K, at the high-fluence irradiation test facility (HIT facility), University of Tokyo. No void swelling was found at any temperature in the neutron irradiated specimens. X-ray energy dispersive spectroscopy revealed that precipitate structure is quite stable below 679 K, while it changed significantly at 793 K. Cavities were formed by charged particle irradiation only after exposure of more than 100 dpa. Helium implantation resulted in very small volume changes in the martensitic phase even at 200 dpa and demonstrated the excellent swelling resistance of JFMS.