Multiple-mechanism and microstructure-based crystal plasticity modeling for cyclic shear deformation of TRIP steel

Abstract

The transformation-induced plasticity (TRIP) steel has an excellent synergy between strength and ductility and is widely used in industry. Cyclic loading is often seen in its industrial application. Therefore, it is of great significance to study cyclic plastic behavior of the TRIP steel. The TRIP steel's cyclic shear behavior and microstructure evolutions were investigated by mechanical testing, electron backscatter diffraction (EBSD) characterization, and in-situ electron channeling contrast imaging (in-situ ECCI) observation. Then, a multiple-mechanism crystal plasticity constitutive model was developed, considering both dislocation slip and martensitic transformation mechanisms. Furthermore, an isotropic hardening law and a modified kinematic hardening rule were taken into account. The crystal plasticity model was implemented into DAMASK with the spectral method. A polycrystalline RVE with realistic grain morphology was constructed from the EBSD data. The simulations of the TRIP steel under cyclic shear loading showed that the samples under higher strain amplitude exhibit stronger cyclic shear hardening. The activation of the martensitic transformation mechanism promotes cyclic hardening. In grain level, the grains with Taylor factor (related to orientation) between 3.3 and 3.9 can activate more slip systems and have a better cyclic hardening ability. So, the Taylor factor is defined as an indicator describing the cyclic response of individual grains in polycrystalline materials. Considering the capability of the established modeling framework, it is of great significance to guide the TRIP steel to serve safely and help the microstructural design in grain scale.