Intercritical annealing of cold-rolled ferrite-pearlite steel: Microstructure evolutions and phase transformation kinetics

The manufacturing of Dual-Phase steels includes as a crucial step the annealing cold-rolled ferrite-pearlite (F/P) microstructure, which involves numerous and interacting metallurgical mechanisms, namely recovery/recrystallization ferrite, globularization, manganese enrichment, coarsening cementite finally austenite transformation. Present study focuses on transformation considering its interaction with ferrite recrystallization influence chemical composition cementite. behavior F/P microstructure is studied at three heating rates to induce weak strong interactions between in particular using post mortem observations but also situ High Energy X-Ray Diffraction experiments synchrotron beamline. Slow leads necklace distribution whereas fast conducts banded topology. This morphogenesis explained by presence intergranular (or isolated) carbides inside matrix, inherited from hot-rolling. Thermokinetic analysis accounting for shows that pearlite islands necessarily partition substitutional elements. Conversely, dissolving isolated undergo partition/partitionless transition heating. After dissolution cementite, final ferrite/austenite takes place. phase kinetics increases increasing rates, despite thermal-activated nature growth process. interpreted thanks kinetic simulations DICTRA software, allow analyze regimes involving or not alloying