Analysis of banded morphology in multiphase steels based on a discrete dislocation-transformation model

The influence of the austenitic microstructural morphology on the mechanical response of a multiphase steel is analyzed by comparing two relevant configurations, namely (i) uniformly distributed grains of retained austenite embedded in a ferritic matrix and (ii) a banded morphology of the two phases. The analysis is carried out numerically using a discrete dislocation-transformation model that captures processes occurring at sub-grain length scales connected to nucleation and evolution of individual dislocations and martensitic platelets inside the austenitic grains. The simulations indicate that a microstructure composed of uniformly distributed grains of austenite is optimal in terms of strength since it delays the onset of plastic localization compared with banded microstructures.