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An Fe-0.2C-5Mn-2.5Al 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 Lüders bands and type A Portevin-le-Châtelier (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 Lüders 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 . and high strain rate performance of TRIP steels. 34Proper characterization of the kinetics of the TRIP effect in a particu-35 lar alloy requires the volume fraction of retained austenite to be measured 36 as a function of strain. This is notoriously difficult to do, however, as dif-37 2 ferent retained austenite volume fraction measurement techniques can give 38 very different values for similar alloys [11, 12]. Determination of the austen-39 ite content is nonetheless critical in alloy design, as it would provide the 40 metallurgist control over the strain hardening contributions from TRIP and 41 TWIP. Attempts have been made to measure the austenite volume fraction 42 as a function of strain by X-ray diffraction (XRD) [13] and magnetization 43 measurements using a ferritescope [13][14][15] in order to quantify TRIP kinet-44 ics. While in terms of the accuracy of the measurement method, magnetic 45 measurements provide no advantage over other methods [12], the primary 46 interest of the method as employed herein is the extremely high sampling 47 rate compared to, for example, XRD or EBSD. It enables one to measure 48 the retained austenite volume fraction in-situ without having to pause the 49 mechanical test, which would not be possible if one wishes to perform the 50 test at the very high strain rates used during stamping operations for exam-51 ple. Sampling rates this high are not normally obtainable by other in-situ 52 methods, making magnetic saturation measurements the unique choice for 53 such an application if the experimenter wants intermediate points between 54 the unstrained and ruptured states. Moreover, a more complete description 55 of the kinetics of TRIP using several hundreds or thousands of experimental 56 data points would make it possible to refine existing TRIP models used in 57 simulations of mechanical behavior. 58 Recent studies on Medium Mn steels have noted that strain hardening 59 is sometimes unstable and that long Lüders plateaus are often observed in ...

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