Nano-bainite transformation and tempering behaviors studied by in situ neutron diffraction

その場中性子観察によるナノベイナイトの変態及び焼き戻しの挙動

Gong, W.; Harjo, S.   ; Koo, M. S.*; 西島 ひかり*; 相澤 一也  ; 友田 陽

Gong, W.; Harjo, S.; Koo, M. S.*; Nishijima, Hikari*; Aizawa, Kazuya; Tomota, Yo

Recently, a special type of bainite steel which is called "Nano-bainite", exhibits a very strong tensile strength of 2.3 GPa and a high toughness of 30 MPa m. The nano-bainite consists of nano-sized lamellar bainitic ferrite, carbon-enriched retained austenite, in which untransformed austenite regions are also observed, and bulky austensite with low carbon concentration. In this study, the bainite transformation behavior during isothermal holding and the stability of the retained austenite at the tempering were examined using an in situ combination observation by neutron diffraction and dilatometry measurement. This method was found to be very useful to observe the nanobainite transformation behavior, and a relation of results obtained from both techniques was clarified.