Investigation of the Effect of Deformation on γ‐α Phase Transformation Kinetics in Hot‐Rolled Dual Phase Steel by Phase Field Approach

Abstract

Dual phase steels, consisting of hard martensite particles in a ductile ferritic matrix, offer high strength and deformability at the same time. Additionally, they are cost effective by a dilute alloying concept. In industrial production, two manufacturing concepts have been implemented: intercritical annealing of cold rolled sheet, or hot rolling. The current work has investigated the effect of deformation on the γ-α phase transformation kinetics in the dual phase steel production using the hot rolling scheme. The pancaked austenite grains containing denser nucleation sites have a strong influence on the ferrite transformation kinetics. In addition, the multiplication of dislocations which results in the increase in elastic strain energy and dislocation core energy contributes to some acceleration in ferrite growth kinetics. A modelling approach for the γ-α phase transformation kinetics in dual phase steels has been developed employing the phase field theory. The nucleation behaviour, i.e. the number and size of nuclei developed after an elapsed time as well as their nucleation sites which were evaluated from microstructure analysis, and the increase in the driving force of grain growth were integrated into this model.