ABSTRACT
In this chapter, both tensile deformation and strain hardening were investigated in detail in an as-annealed dual-phase steel. The microstructural origin of hetero-deformation induced (HDI) stresses was ascribed to plastic mismatches near grain/phase boundaries between two phases as evidenced by the change of Schmid factor and Kernel Average Misorientation values. The production of geometrically necessary dislocations was responsible to both HDI stress and HDI hardening, which accounted for a large proportion of global flow stress and strain hardening. Large mechanical mismatch makes it an ideal dual-phase microstructure to reveal the formation and evolution of both back stress and HDI hardening during tensile deformation. A universal microstructure-based model is developed to describe the evolution of back stress in a dual phase microstructure. The back stress predicted by the model is well consistent with that by experimental measurements. In terms of the model, the back stress will increase by both increasing volume fraction in B2 phase and decreasing grain sizes.
