Effect of microstructural evolution on deformation behaviour of pre-strained dual-phase steel

The influence of microstructural evolution on the strain hardening and non-uniform deformation behaviour of pre-strained ferrite-martensite DP steel was studied using a crystal plasticity finite element method (CPFEM). The material parameters in the CPFEM were identified through a systematic procedure by fitting models to the experimental results of micro-tensile tests. The CPFEM with the identified parameters were applied to the analysis of virtual models with focus on the microstructural factors such as the angle of interphase boundary, the orientation of habit plane in the martensite phase, and the intensity of texture in the ultrafine-grained ferrite phase developed in the severely-deformed sample. The analysis results suggested the following influences of microstructural factors on the deformation behaviour. The formation of deformation bands in the ferrite phase depends on the configuration of the interphase boundary, the orientation of the habit plane in neighbouring martensite phase and the intensity of texture in the ferrite phase. The suppressions of the deformation bands by controlling microstructure could contribute to later onset of necking and resultant higher strain hardening.