Host: The Iron and Steel Institute of Japan
Pages 119-128
Deformation-induced martensitic transformation (DIMT) during various plastic deformations of the bainitic steels with three different carbon contents was studied. The initial microstructures were prepared by the austempering at the same holding temperature (400°C), and they were identified as bainite consisting of bainitic ferrite and the retained austenite whose volume fraction was larger with the larger carbon content. In all of three steels, the compressive deformation showed lower work hardening than the tension. The measurement of both electron back scattering diffraction (EBSD) and in situ neutron diffraction confirmed the less reduction of retained austenite at the compression, indicating the primary reason for the change in work hardening behaviors. In addition, the change in the reduction of retained austenite was observed along the thickness of the bent steels with the different carbon contents because of the change in hoop stress polarity along the thickness. The mechanism of the DIMT dependence on the carbon content and the stress polarity is discussed with deformation texture and the crystallographic orientation dependence on DIMT.
