FEM modeling of flow curves for ferrite/pearlite two-phase steels

Flow curves of ferrite/pearlite two-phase steels were simulated using finite element method (FEM) with regression equations for flow curves of each ferrite and pearlite phase proposed by Hiramatsu et ai. and Furukawa et ai. The calculated flow strength of ferrite/pearlite two-phase steel was lower than the experimentally measured one mainly due to the underestimation of flow strength of ferrite phase according to the yield elongation. To improve the simulation, the flow curves in homogeneous deformation range were considered. Microscopic observations revealed that most deformation was accumulated in the ferrite phase during yield elongation. Flow curves of ferrite phase were re-evaluated based on this observation and flow curves of ferrite/pearlite steels were also re-calculated. Re-calculated yield strength of ferrite/pearlite steels showed good agreement with measured ones, however the work hardening rate of re-calculated flow curves is still lower than that of measured one. The simplicity of pearlite morphology for FEM analysis is thought to be responsible for lower work hardening behavior of calculated flow curve by FEM than that of measured one.