Interpretation of the Unloading Non-linearity in Dual-Phase 980 Steel Using an Elasto-Visco-Plastic Self-consistent Polycrystal Model

A dual-phase 980 steel sample consisting of hard martensitic and ductile ferritic phases was investigated in terms of its nonlinear unloading behavior and the Bauschinger effect. The microstructural characters obtained from a set of electron back-scattered diffraction scans were used to analyze the crystallographic texture for each phase. The incremental elasto-visco-plastic self-consistent model was applied with an empirical Voce hardening law. Neither backstress nor the effect of geometrically necessary dislocation was accounted for. Despite the simplicity of this baseline \(\Delta \) EVPSC model, the nonlinear unloading and the Bauschinger effect were captured. It seems that the contrast in the critical resolved shear stress of the two phases suffices to induce earlier and selective re-yielding of ductile ferrite.