The ratchetting and retained austenite transformation of medium‐manganese transformation‐induced plasticity steel during asymmetrical cyclic stressing

The uniaxial ratchetting behavior and cyclic softening/hardening characteristics of Fe-0.4C-7Mn-3.2Al steel are revealed by cyclic loading experiments. Electron backscattered diffraction (EBSD) and X-ray diffraction (XRD) analyses have been carried out for assessing retained austenite (RA) transformation during cyclic deformation. Fe-0.4C-7Mn-3.2Al steel exhibits a gradual transition from cyclic stabilization to slight cyclic hardening with increasing strain amplitude. RA transformation is one of the reasons for cyclic hardening. The ratchetting of Fe-0.4C-7Mn-3.2Al steel shows two different characteristics under asymmetrical cyclic stressing. When the stress amplitude is below a certain value, the ratchetting is similar to that of typical cyclic stabilized materials in three stages of deceleration, stabilization and acceleration. However, when the stress amplitude reaches a certain level, the ratchetting evolution accelerates from the beginning to the fracture. The results show that the interaction between transformation-induced plasticity and ratchetting strain can lead to accelerated accumulation of plastic strain.