Role of retained austenite and deformation-induced martensite in 0.15C-5Mn steel monitored by neutron diffraction measurement during tensile deformation

Yamashita, Takayuki*; Morooka, Satoshi  ; Gong, W.   ; Kawasaki, Takuro   ; Harjo, S.   ; Hojo, Tomohiko*; Okitsu, Yoshitaka*; Fujii, Hidetoshi*

An Fe-0.15C-5Mn-0.5Si-0.05Nb steel annealed at 660C and 685C showed Lders deformation followed by high work hardening, with variations in Lders strain and hardening behavior. neutron diffraction during tensile tests analyzed phase stresses, strength contributions, and austenite orientation. Deformation-induced martensite contributed 1000 MPa to strength near tensile failure, while austenite mainly enhanced ductility via transformation-induced plasticity. Austenite transformed to martensite during Lders deformation regardless of orientation, though 311-oriented grains tended to remain along the tensile direction.