Relationship between crack growth rates and locally deformed structures in irradiated 316L stainless steels

Chimi, Yasuhiro; Kasahara, Shigeki; Nishiyama, Yutaka ; Seto, Hitoshi*; Kitsunai, Yuji*; Koshiishi, Masato*

In order to understand irradiation-assisted stress corrosion cracking (IASCC) growth behavior, crack growth tests using compact tension (CT) specimens made of neutron-irradiated 316L stainless steels (SSs) were performed in simulated BWR environments (at 288C). Moreover, microstructures of deformed areas were observed by transmission electron microscope (TEM) after straining tensile specimens made of neutron-irradiated 316L SSs. As a result, for lower neutron dose than 1.9 dpa, the crack growth rates (CGRs) show effective environmental mitigation and the deformed structures show tangling of dislocations. On the other hand, for higher neutron dose than 2.7 dpa, the CGRs show small environmental mitigation and the deformed structures consist mainly of dislocation channels. From the relationship between CGRs and deformed structures, mechanisms on IASCC growth will be discussed.