Effect of microstructure pattern on the strain localization in DP600 steels analyzed using combined in-situ experimental test and numerical simulation

The phenomenon of strain localization is considered the most effective cause of failure in dual phase steels. In the present study, we have performed in-situ tensile tests to investigate the strain localization in ferrite phase. In order to quantify the level of microscopic deformation, an image processing code was used and the the strain map was subsequently superimposed onto the scanning electron microscopy (SEM) image obtained from the in-situ test. The SEM image that was captured during the in-situ tensile test was further used in a finite element dislocation density model, based on which the similarities and differences between the experimental and simulation results were discussed. The amount of localized deformation in the ferrite phase was found to be much higher in the regions between martensite islands. A parametric study was then performed to gain deeper insights on the effect of martensite grain size on the strain localization of the neighboring ferrite. Furthermore, using the experimental results, the localization of strain inside the high deformational fields before the final failure was discussed.