Effect of phase content on deformation compatibility in ferrite and bainite dual-phase steel: experimental and crystal plasticity finite element analysis

The phase volume fraction has an important role in the match of the strength and plasticity of dual phase steel. The different bainite contents (18–53 vol.%) in polygonal ferrite and bainite (PF + B) dual phase steel were obtained by controlling the relaxation finish temperature during the rolling process. The effect of bainite volume fraction on the tensile deformability was systematically investigated via experiments and crystal plasticity finite element model (CPFEM) simulation. The experimental results showed that the steel showed optimal strain hardenability and strength–plasticity matching when the bainite reached 35%. The 3D-CPFEM models with the same grain size and texture characters were established to clarify the influence of stress/strain distribution on PF + B dual phase steel with different bainite contents. The simulation results indicated that an appropriate increase in the bainite content (18%–35%) did not affect the interphase strain difference, but increased the stress distribution in both phases, as a result of enhancing the coordinated deformability of two phases and improving the strength–plasticity matching. When the bainite content increased to 53%, the stress/strain difference between the two phases was greatly increased, and plastic damage between the two phases was caused by the reduction of the coordinated deformability.