The micromechanical deformation behaviors of hot-rolled 590FB steel during hole-expansion test

The crystal plasticity finite element method (CPFEM) was used to study the effect exerted by the crystallographic orientation and spatial distribution of the constituent phases in 590FB steel during hole-expansion. The individual crystallographic orientations and spatial distributions for ferrite and bainite phases in 590FB steel was characterized using phase identification method that combined optical microstructure and EBSD data. By a direct mapping of the microstructure into finite element meshes, the CPFEM captured the effect of the microstructure heterogeneity on the hot spots for void formation and micro-crack propagation in 590FB steel during hole-expansion. The void formation mechanisms as well as micro-crack propagation were analyzed through hierarchical scanning electron microscope (SEM) observations at the hole edge. An isotropic elasto-plastic FEM was also used to simulate the micromechanical deformation behaviors of 590FB steel during hole-expansion without considering the crystallographic orientation of the constituent phases. The simulation results demonstrated that the initial crystallographic orientation of the constituent phases significantly affects the hot spots for void formation and micro-crack propagation in 590FB steel during hole-expansion.