A comprehensive study of microstructure evolution for a Mo-TRIP (transformation-inducedplasticity) steel under hot strip rolling conditions has been conducted. This investigation includes austenite grain growth during reheating, deformation behavior, and static recrystallization kinetics of austenite as well as the effect of cooling rate and austenite conditioning on the continuous cooling transformation (CCT) behavior. The physically based Kocks-Mecking model has been employed to describe the deformation behavior of austenite, while the JohnsonMehl-Avrami-Kolmogorov (JMAK) approach has been used to predict static recrystallization, and an empirical equation has been formulated for the recrystallized austenite grain size. Ferrite transformation start is described by a model considering early growth of corner nucleated ferrite. The fraction of ferrite transformed from austenite during continuous cooling is predicted by the semiempirical JMAK approach in combination with Scheil's equation of additivity. The effect of carbon enrichment on ferrite transformation kinetics is explicitly included in the model. In addition, a phenomenological model for the bainite formation has been proposed. Martensite transformation start is described by an empirical equation taking into account carbon enrichment of remaining austenite. Finally, the entire hot strip rolling and controlled cooling process have been simulated by hot torsion tests, and the optimum coiling temperatures for the formation of TRIP microstructures have been determined.
The correlation between the strain-induced martensite transformation (SIMT) and the Portevin-Le Chatelier (PLC) effect during tensile testing of a ferrite-austenite duplex medium manganese (Mn) steel was investigated in this study. A discontinuous SIMT phenomenon (D-SIMT) was observed in the steel by in situ magnetic induction measurements complemented with ex situ X-ray diffraction analysis. This unique behavior was due to the localized martensite formation in the PLC bands forming and propagating continuously during tensile straining. The PLC bands were characterized by the digital image correlation technique and their origin is further discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.