Computational modeling of the effect of equiaxed heterogeneous microstructures on strength and ductility of dual phase steels

Abstract In this study, a code was developed to create virtual random representative volume elements (RVEs) depicting the actual and highly equiaxed heterogeneous microstructure of ferrite-martensite dual phase (DP) steels. Within this approach it was possible to perform a parametric study of the effects of DP microstructure (e.g., volume fraction, size, and distribution of the martensite; grain size and boundaries of the ferrite; martensite-ferrite interphase) and mechanical properties of the ferrite and martensite phases on the overall stress-strain behavior. A finite strain elastic-viscoplastic constitutive model has been used in conducting these microstructural-based simulations. It is shown that plastic strain localization in the form of localized narrow bands significantly control the ductility and ultimate fracture of DP steels. It was also noticed that by adding viscosity into the material property, the ductility increased significantly without compromising the strength of DP steels. It is shown that by decreasing the size of martensite phase and considering the ferrite-martensite interphase the overall response yields a simultaneous increase in strength and ductility.