In Situ EBSD Observation and Numerical Simulation of Microstructure Evolution and Strain Localization of DP780 Dual-Phase Steel

Abstract

To reveal the microstructural evolution and stress–strain distribution of 780 MPa-grade ferrite/martensite dual-phase steel during a uniaxial tensile deformation process, the plastic deformation behavior under uniaxial tension was studied using in situ EBSD and crystal plastic finite element method (CPFEM). The results showed that the geometrically necessary dislocations (GND) in ferrite accumulated continuously, which is conducive to the formation of grain boundaries, but the texture distribution did not change significantly. The average misorientation angle decreased and the proportion of low-angle grain boundaries increased with the increase of strain. At high strain, the plastic deformation mainly occurred in the soft ferrite region within a 45° distribution from the loading direction. In the undeformed state, the texture of the dual-phase steel was characterized by α-fibers and γ-fibers. Interfacial debonding was caused by the accumulation of geometrically necessary dislocations. The fracture morphologies showed that the specimens had typical ductile fracture characteristics.