Coincidence of strain-induced TRIP and propagative PLC bands in Medium Mn steels

An Fe-0.2C-5Mn-2.5A1 medium manganese steel is studied for three different intercritical annealing temperatures T-IA to observe the effects of variations of retained austenite stability on the mechanical work hardening in uniaxial tension. Digital image correlation (DIC) showed that both Lfiders bands and type A Portevin-le-Chatelier (PLC) bands occurred in samples with a lower T-IA, but both disappeared when T-IA was increased. In-situ measurements of sample magnetization with a correction for stress effects on the magnetic properties of the sample allowed for continuous measurement of the retained austenite volume fraction. This method provided a complete characterization of the kinetics of transformation-induced plasticity (TRIP) in the sample over the course of tensile testing. It is shown that the martensite transformation was purely strain -induced and coincided with the passage of both Liiders and PLC bands. An Olson -Cohen model was applied to magnetic data to attempt to explain the differences in TRIP kinetics with varying T-IA.