Elucidating the effect of Mn partitioning on interface migration and carbon partitioning during Quenching and Partitioning of the Fe-C-Mn-Si steels: Modeling and experiments

A fundamental understanding of carbon partitioning and the martensite/austenite interface migration during the Quenching & Partitioning (Q&P) process is essential for tailoring the microstructures of the advanced Q&P steels. In this study, two Q&P models (QP-LE and QP-PE), in which effects of substitutional alloying elements have been considered by assuming Local Equilibrium (LE) or Paraequilibrium (PE) at the interface, are proposed to simulate the kinetics of martensite/austenite interface migration and carbon partitioning in the Fe-C-Mn-Si steels. The QP-LE and QP-PE models predict that whether the interface migrates or not and its moving direction are dependent on quenching/partitioning temperature (QT/PT) and alloy composition. A careful comparison between experiments and model predictions indicates that the dependence of interface migration behavior on QT/PT indirectly measured by experiments during the Q&P process could be explained reasonably well by the QP-LE model, rather than the Constrain Carbon Equilibrium (CCE) model and the QP-PE model. The carbon partitioning behavior is also well predicted by the QP-LE model while the QP-PE model predictions deviate significantly from experiments. The current study suggests that interfacial partitioning of Mn plays a significant role in carbon partitioning and interface migration during the Q&P process. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.