Mechanical behavior and microstructural evolution of Fe-22Mn-C TWIP/TRIP steels as a function of C content

TRIP/TWIP steels are promising candidate materials for the automotive industry due to their high strength and ductility. During deformation, these steels transform by creating twin boundaries (TWIP) or by austenite transforming to s-martensite (TRIP). By lowering the carbon content from 0.6wt% to 0.2wt%, various TWIP/TRIP deformation modes were achieved. The mechanical response was analyzed as a function of microstructural evolution, work hardening and the relative contributions of kinematic versus isotropic hardening. The microstructural evolution versus carbon content was observed at a variety of length scales in order to detect features such as austenite, ε-martensite, twins and stacking faults. The 0.6wt%C TWIP steel had high strength and ductility and transformed primarily through the production of twin boundaries. The 0.4wt%C steel produced both twin boundaries and s-martensite. The 0.2wt%C TRIP steel exhibited s-martensite transformation with high strength and low ductility.