Evaluation of locally deformed step structure in austenitic stainless steel irradiated with neutrons

Kitsunai, Yuji*; Kasahara, Shigeki; Chimi, Yasuhiro; Nishiyama, Yutaka ; Chatani, Kazuhiro*; Koshiishi, Masato*

In order to consider mechanism on irradiation-assisted stress corrosion cracking (IASCC), oxide films on surface of locally deformed structure in irradiated stainless steel are investigated. The miniature tensile specimens are made of 316L stainless steels irradiated with neutrons in the Japan Materials Testing Reactor (JMTR). The specimens are strained up to 0.1-2%, and surface structure and crystal misorientation among grains are observed by scanning electron microscope (SEM) and electron backscattering diffraction (EBSD). As a result, visible step structure due to slip plane is appeared on the specimen surface, depending on the neutron fluence and the applied strain level. Furthermore, the data from EBSD suggests that the localization of strain occurred in the vicinity of grain boundaries. The visible step structure characterized from the viewpoints of the morphology and density, and the effects of neutron fluence and stain are discussed on the step structure are discussed.