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*

A Fe-0.15C-5Mn-0.5Si-0.05Nb medium Mn steel annealed at 660C and 685C both exhibited inhomogeneous deformation with Luders deformation and extremely high work hardening rates, but with different Luders strain and work hardening behavior. neutron diffraction measurements during tensile test were performed to investigate changes in the phase stresses and in the contributed stresses to the strength of the constituent phases, and crystal orientation of austenite. The role of each constituent phase in the deformation and the effect of crystallographic orientation on austenite stability were discussed. Deformation induced martensite showed excellent phase stress and contributed to the strength approximately 1000 MPa, which is close to macroscopic tensile strength.