In-situ study of tensile deformation behaviour of medium Mn TWIP/TRIP steel using synchrotron radiation

This investigation proposes a pathway for generating optimum microstructure for a medium Mn containing twinning-induced plasticity/transformation-induced plasticity (TWIP/TRIP) steels. The steel contains a two-phase microstructure consisting of austenite and ferrite phase arranged in a lamellar fashion. The microstructure was developed following a specially designed thermo-mechanical processing schedule that involved quenching and partitioning. The feedback for the design of thermo-mechanical processing was obtained by carrying out in-situ deformation in high energy synchrotron radiation under tensile loading. Diffraction patterns were analysed for estimating the retained austenite phase fraction and other aspects of microstructural evolution. X-ray line profile analysis was performed to determine crystallite size, dislocation density, and twin density at individual stages of deformation. In the early stages, deformation occurs by dislocation slip in both phases, while in the later stages, deformation in the austenite phase occurs via twinning and martensitic transformation, and in the ferrite phase by dislocation slip. Strain hardening behaviour has been analysed and correlated with microstructural parameters.