EBSD analysis of fracture behaviour of cast duplex stainless steels used in JAEA's nuclear reactor Fugen

Takeuchi, Tomoaki   ; Nogiwa, Kimihiro*; Sakakibara, Yasuhide*; Tsuchiya, Kunihiko 

Analyses on fracture behavior of cast duplex stainless steels sampled from piping of primary loop recirculation system of JAEA's nuclear reactor Fugen were performed. The samples were composed of primary austenite phase, and minor ferrite phase with from a few to few tens percent of volume fraction. It is known that thermal aging at about 300-500C causes hardening of only the ferrite phase. Therefore, electron back-scattered diffraction (EBSD) analysis, which can observe individually the properties of the two phases, was applied so as to reveal its fracture mechanism. The results indicated that the crystallographic orientation relationship between the austenite and ferrite was hybrid, and that the Charpy absorbed energy depended on the deformation behavior of not only the austenite phase but also the minor ferrite phase near the fracture surface.