Intragranular Ferrite Nucleation on MX Carbonitrides and Dislocations

The competing mechanisms of ferrite nucleation on (Ti,V)(C,N) MX carbonitrides and dislocations, as well as their dependence on deformation, are investigated experimentally by thermo-mechanical treatments and via simulation. The impact of recrystallization and the resulting austenite grain size on intragranular ferrite nucleation is evaluated. The austenite-to-ferrite transformation temperatures, affected by different microstructures, are examined by isothermal uniaxial single-hit compression tests on a dilatometer DIL 805 and compared to thermal treatments without deformation. Different resulting microstructures are analyzed by using optical light microscopy. The experimental data is used for the validation of thermo-kinetic simulations with the mean-field modeling software MatCalc using the implemented models for the austenite grain evolution, the on-particle nucleation of ferrite on the surface of MX particles, the dislocation density evolution, and recrystallization.