Microstructure evolution of T91 irradiated in the BOR60 fast reactor

• Published in: Journal of nuclear materials 2018-06, Vol.504, p.122-134
• Main Authors: Jiao, Z., Taller, S., Field, K., Yeli, G., Moody, M.P., Was, G.S.
• Format: Article
• Language: English
• Subjects: Bubbles; Cavities; Chromium; Copper; Dislocation; Dislocation loops; Enrichment; GENERAL STUDIES OF NUCLEAR REACTORS; Grain boundaries; Holes; Irradiation; MATERIALS SCIENCE; Microstructure; Precipitates; Proton irradiation; Radiation; Radiation effects; Radiation-induced precipitates; Radiation-induced segregation; Reactors; Scanning electron microscopy; Scanning transmission electron microscopy; Segregation; Silicon; Swelling; Temperature; Temperature dependence; Temperature effects; Transmission electron microscopy
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2018.03.024

Microstructures of T91 neutron irradiated in the BOR60 reactor at five temperatures between 376 °C and 524 °C to doses between 15.4 and 35.1 dpa were characterized using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and atom probe tomography (APT). Type a dislocation loops were observed at 376–415 °C and network dislocations dominated at 460 °C and 524 °C. Cavities appeared in a bimodal distribution with a high density of small bubbles less than 2 nm at irradiation temperatures between 376 °C and 415 °C. Small bubbles were also observed at 460 °C and 524 °C but cavities greater than 2 nm were absent. Enrichment of Cr, Ni, and Si at the grain boundary was observed at all irradiation temperatures. Radiation-induced segregation (RIS) of Cr, Ni and Si appeared to saturate at 17.1 dpa and 376 °C. The temperature dependence of RIS of Cr, Ni and Si at the grain boundary, which showed a peak Cr enrichment temperature of 460 °C and a lower peak Ni and Si enrichment temperature of ∼400 °C, was consistent with observations of RIS of Cr in proton irradiated T91, suggesting that the same RIS mechanism may also apply to BOR60 irradiated T91. G-phase and Cu-rich precipitates were observed at 376–415 °C but were absent at 460 °C and 524 °C. The absence of G-phase at 524 °C could be related to the minimal segregation of Ni and Si in that condition.