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Effects of dose rate change under irradiation on hardening and microstructural evolution in A533B steel |
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| Authors: | Katsuhiko Fujii Koji Fukuya Tomohiro Hojo |
| Affiliation: | 1. Institute of Nuclear Safety System, 64 Sata, Mihama-cho, Mikata-gun , Fukui , 919-1205 , Japan fujiik@inss.co.jp;3. Institute of Nuclear Safety System, 64 Sata, Mihama-cho, Mikata-gun , Fukui , 919-1205 , Japan;4. Japan Nuclear Energy Safety Organization, 3-17-1, Toranomon, Minato-ku , Tokyo , 105-0001 , Japan |
| Abstract: | Iron-ion irradiations were carried out for 0.09wt%Cu A533B steel specimens at 290°C to investigate effects of dose rate change during irradiation; the irradiations consisted of the base irradiation (with an unchanged dose rate) and an additional one with changed dose rates from 1 to 50 times that of the base one. Nano-indentation hardness measurements showed that the increase in hardness was higher for lower dose rate of the base irradiation. A similar trend was identified during the additional irradiation. Transmission electron microscope (TEM) and three-dimensional atom probe (3DAP) analyses were carried out for the quantitative characterization of defect features. Mn/Ni/Si/Cu-enriched clusters and dislocation loops were observed in all specimens. The increase in hardness mainly depended on the formation of the solute atom clusters. The square root of the volume fraction of the solute atom clusters provided a good correlation with the increase in hardness. The effects of dose rate and dose rate change during irradiation were explained by the formation of solute atom clusters. |
| Keywords: | dose rate effect ion irradiation hardening solute atom cluster dislocation loop embrittlement reactor pressure vessel nano indentation atom probe transmission electron microscopy |