Micromechanical analysis of two heat-treated dual phase steels: DP800 and DP980

Dual phase (DP) steels, which have an intricate microstructure, consist of ferrite and martensite phases and because of interaction between the ferrite and martensite phases, those have complex behaviors. In this study, the flow curves of two heat-treated DP steels, DP800 and DP980, were compared with those of the 2D and 3D micromechanical models based on actual microstructure under symmetric and periodic boundary conditions. The effects of martensite phase distributions on the flow curves of 2D and 3D micromechanical models were investigated. Moreover, two different microstructures of DP980 with two different distributions of martensite phases were compared together to investigate the effect of martensite phase distribution in 2D and 3D micromechanical models on the stress-strain curve of DP980. Also, an in-situ tensile setup test was employed in order to investigate the initiation of localized strain patterns in the ferrite phase. The stress-strain curve, localization patterns and initiation of slip bands obtained from 2D and 3D micromechanical models were compared with the experimental results. The numerical results revealed that the stress-strain curves obtained from 3D models in comparison with 2D models are in closer agreement with experimental data.