Effect of strain rate and temperature on the serration behavior of SA508-III RPV steel in the dynamic strain aging process
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Dynamic strain aging (DSA) effect on SA508-III reactor pressure vessel (RPV) steel was investigated. The SA508-III RPV steel was subjected to tension tests at different strain rates (1.1 × 10−5 s−1 and 6.6 × 10−5 s−1) and different temperatures (500 and 550 °C) to evaluate the influence of strain rate and temperature on the serrated flow behavior, which is the repetitive and discontinuous yielding phenomenon on the stress–strain curves. The higher temperature leads to the higher density of precipitates, M23C6 carbides and needle-like Mo2C carbides. It was found that the samples under tension test of 6.6 × 10−5 s−1 and 500 °C possess superior mechanical properties and mainly show A-type serrations on the tension test curves. Then, the local regress method was used to filter the DSA curves, thus to show the real trend of the curves. It has been found that the less time of interaction between dislocations and precipitates under higher strain rates leads to a higher strength of the sample. The more tiny-stress drops on the 550 °C serration curve can be attributed to the hardening phase, M23C6 carbides and needle-like Mo2C carbides. The higher percentage of the small stress drops on the serration curves represents the higher mechanical strength.
KeywordsReactor pressure vessel steel SA508-III steel Dynamic strain aging Serration behavior
This work is financially supported by the National Science and Technology Key Specific Project: Life Management Technology of Nuclear Power Plant of China (Grant No. 2011ZX06004-002). The authors would like to express thanks for the help with the manufacturing of the SA508-III reactor pressure vessel steel by Shougang Technology Research Institute.
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