Mesoscale Deformation Incompatibility Analysis of DP1180 Steel

Abstract: Advanced high-strength steel (AHSS) is of great technological interest in automotive lightweight applications. The dual-phase (DP) steel with a higher volume fraction of martensite has been rarely studied. In this work, the micromechanical deformation incompatibility of DP1180 steel was analyzed by a microstructure-based representative volume element (RVE) model. Via the electron-backscattered diffraction (EBSD) and the open-source software DREAM.3D, the statistically real microstructure-based RVE model was established. The flow curve of ferrite was obtained by the dislocation-based method. And the flow curve of martensite was obtained by the isostrain method (ISM) and the non-isostrain method (NISM). The simulation results showed good coincidence with the experiments. Furthermore, the ISM and the NISM were well clarified and improved. The microscale stress and strain in ferrite and martensite are approximately normal distributions due to the deformation incompatibility. The simulations verified that martensite carries much higher stress than ferrite. The mean value of strain in martensite is smaller than that in ferrite. And the strain variances of ferrite and martensite are similar. A larger variation range of stress triaxiality in ferrite indicates that the ferrite has gone through a more complex stress state. While the martensite has been approaching from the tension–compression state to the uniaxial-tension state. Consequently, the strain localization and damage initiation are predicted to be preferentially through ferrite compared to martensite, which is in good agreement with the results of the in situ tensile test. This paper provides a detailed analysis of the deformation incompatibility of the DP steel, especially in which the volume fraction of martensite is larger than that of ferrite. And it has theoretical significance for accurately predicting the micromechanical deformation behavior of multi-phase materials. Graphical Abstract: [Figure not available: see fulltext.]