SEDL / STP / STP1046V2-EB / STP49463S

Response of Ferritic/Martensitic Steels to Neutrons at Irradiation Temperatures from 20 to 823 K

Kohyama, Akira
Associate professor, The University of Tokyo, Tokyo,

Hamada, Kazusi
Graduate student, The University of Tokyo, Tokyo,

Asakura, Kentaro
Research associate, The University of Tokyo, Tokyo,

Matsui, Hideki
Professor, Tohoku University, Sendai-City Miyagi,

Pages: 18    Published: Jan 1990

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Abstract

The objectives of this work are to evaluate mechanical property changes by means of small specimen testing techniques, to evaluate the influence of the cascade damage produced by 14-MeV neutrons from RTNS-II on microstructural evolution, and to understand mechanical property changes in term of microstructural evolution at irradiation temperatures of from 20 to 823 K.

The fluence dependence of mechanical properties showed a trend towards irradiation hardening for room temperature and for low temperature irradiations. At elevated temperatures, radiation softening was observed. The transition from hardening to softening was chemical composition sensitive and was closely related to microstructural developments. The fluence dependence of the irradiation hardening could be understood as dispersion hardening from irradiation-induced complex defects. The temperature dependence of yield stress for 20 K irradiated specimens suggested that the thermal component of yield stress can be understood also by a dispersion hardening mechanism resulting from defect clusters. The thermal component of irradiation hardening was dominant in 20-K irradiated specimens, and was virtually annealed out at room temperature. On the other hand, 300 K irradiation mainly produced an athermal component of irradiation hardening, which was about half of that for 20 K irradiated specimens.