Radiation response of alloy T91 at damage levels up to 1000 peak dpa

Abstract

Ferritic-martensitic alloys are required for advanced reactor components to survive 500-600 neutron-induced dpa. Ion-induced void swelling of ferritic-martensitic alloy T91 in the quenched and tempered condition has been studied using a defocused, non-rastered 3.5 MeV Fe-ion beam at 475°C to produce damage levels up to 1000 peak displacements per atom (dpa). The high peak damage level of 1000 dpa is required to reach 500-600 dpa level due to injected interstitial suppression of void nucleation in the peak dpa region, requiring data extraction closer to the surface at lower dpa levels. At a relatively low peak damage level of 250 dpa, voids began to develop, appearing first in the near-surface region. With increasing ion fluence, swelling was observed deeper in the specimen, but remained completely suppressed in the back half of the ion range, even at 1000 peak dpa. The local differences in dpa rate in the front half of the ion range induce an "internal temperature shift" that strongly influences the onset of swelling, with shorter transient regimes resulting from lower dpa rates, in agreement not only with observations in neutron irradiation studies but also in various ion irradiations. Swelling was accompanied by radiation-induced precipitation of Cu-rich and Si, Ni, Mn-rich phases were observed by atom probe tomography, indicating concurrent microchemical evolution was in progress. In comparison to other ferritic-martensitic alloys during ion irradiation, T91 exhibits good swelling resistance with a swelling incubation period of about 400 local dpa.

Fundamental Studies of Irradiation-Induced Modifications in Microstructural Evolution and Mechanical Properties of Advanced Alloys

“…The swelling approaches 0 for regions over ∼800 nm, where the injected ions are distributed. This kind of suppressed swelling behavior in the injected ion region has also been reported by many previous studies on self-ion irradiated F/M steels and ODS F/M steels [78,79], and can be well-explained by the defect imbalance and injected interstitials [80,81]. For comparison, Fig.…”

Beam-contamination-induced compositional alteration and its neutron-atypical consequences in ion simulation of neutron-induced void swelling

“…Ion irradiation was performed using 3.5 MeV Fe 2+ ions. A defocused ion beam was utilized to produce a static beam with a 10-15% variation in uniformity across the beam and a time-averaged peak dpa rate of 1.74 × 10 −3 dpa/s maintained within ±5% over the duration of the irradiation [9,18]. Specimens were fixed to the stage using a carbon-free silver paste (Ted Pella, Inc.…”

“…All doses were calculated using the Kinchin-Pease option of the SRIM-2013 code with a 40 eV displacement energy [19,20]. Transmission electron microscopy (TEM) specimens were prepared using a TESCAN Lyra focused ion beam mill [18]. Scanning transmission electron microscopy (STEM) high-angle annular dark field (HAADF) and bright field images were obtained using an FEI Tecnai F20 Super Twin operated at 200 kV.…”

“…Scanning transmission electron microscopy (STEM) high-angle annular dark field (HAADF) and bright field images were obtained using an FEI Tecnai F20 Super Twin operated at 200 kV. TEM lamella thicknesses were measured using a standard electron energy loss spectroscopy technique and were used to calculate void swelling described in an earlier study [18]. Secondary ion mass spectroscopy (SIMS) results were obtained using a Physical Electronics Model 6600 SIMS System with a 4-keV Cs beam for depth profiling of elemental carbon, oxygen, and nitrogen.…”

Influence of Metal Additives on Microstructure and Properties of Amorphous Metal–SiOC Composites

“…[1][2][3][4] Polycrystalline materials such as austenitic steels have great potential for use in fast reactors but could not reliably serve beyond ~150 displacements per atom (dpa). 5,6 Ferritic and ferritic-martensitic (FM) steels have been found to swell much less than austenitic steels. 7 Nanostructuring of both austenitic and FM steels appears to be a promising avenue for further improvement of swelling resistance, providing that such structures are stable under irradiation.…”