Stress-strain behavior of multi-phase high performance structural steel

A series of ferrite/bainite (F/B) multi-phase steels containing different volume fractions of ferrite were obtained. The effect of soft phase (ferrite) content on the work-hardening behavior of the steel was studied by the finite element simulation with V-BCC model and the modified Crussard-Jaoul (C-J) analysis. It is shown that the multi-phase steels have an excellent anti-deformation ability, such as higher stress ratio (Rt1.5/Rt0.5), higher uniform elongation and lower yield to tensile strength ratio. For the F/B multi-phase steels, increasing the proportion of ferrite would help to increase the uniform elongation. However, introducing much more fraction of ferrite would not be helpful to improve the stress ratio of multi-phase steel. The ferrite plastic strain constrained by bainite would be beneficial to increasing the work hardening rate. The optimum proportion of ferrite will result both higher stress ratio and uniform elongation in multi-phase steel.