Manganese partitioning in low carbon manganese steel during annealing

For 6Mn16 steel experimental soft annealing at 625 °C for periods from 1 h to 60 h and modeling with Thermo-Calc were performed to estimate the partitioning of alloying elements, in particular Mn, between ferrite, cementite and austenite. Using transmission electron microscopy and X-ray analysis it was established that the increase of Mn concentration in carbides to a level 7%–11.2% caused a local decrease of the Ac1 temperature and led to the presence of austenite around the carbides. Thus, after cooling, small bainite–martensite or bainite–martensite-retained austenite (BM-A) islands were observed. A dispersion of carbides and a coarsening process were observed. The measured amount of Mn in the carbides was in good agreement with theoretical predictions.