The Effects of Inhomogeneous Mechanical Properties of the Ferrite Phase on Dual Phase Steel's Behavior

The microstructure of dual phase steels can be considered as a matrix of ferrite phase reinforced by martensite particles. Recent measurements show that the mechanical properties of the ferrite phase are changed with the distance from the martensite grains. In this paper, a new method has been proposed to consider this phenomenon in finite element modeling of dual phase steels microstructure. In this method, ferrite mechanical properties were imported to the model as a continuous function of the distance from martensite boundary. A unit cell model of dual phase steel was constructed based on the experimental measurements. The tensile test was simulated in both cases of considering the ferrite phase as the homogeneous and inhomogeneous matrix. It was observed that by considering the ferrite phase inhomogeneity, the model could predict macro stress precisely. Considering the ferrite phase inhomogeneity also led to the better prediction of shear band formation in the unit cell, as compared to the other model. A different stress distribution prediction was also observed in these two models and ferrite phase maximum stress was higher when inhomogeneity was included. These observations could be crucial in the investigation of dual phase steels damage. It was observed that martensite volume fraction and the grain size had a stronger effect on the model with the inhomogeneous ferrite phase.