Cross-Scale Study of DP780 Steel: From Crystal Plasticity Modeling to Failure and Formability Prediction

Abstract

This study presents a novel cross-scale methodology for accurately predicting the failure behavior and formability of dual-phase (DP) 780 (DP780) steel based on its microstructural features. The steel's microstructure and mechanical properties are characterized via light optical microscopy and uniaxial tensile tests, respectively. Microdamage mechanisms are identified through in situ bending tests, while the results of nanoindentation and electron backscatter diffraction (EBSD) are applied to calibrate crystal plasticity model parameters for the ferrite phase during finite element simulations. Martensite phase properties are determined through uniaxial tensile simulations on a representative volume element. By varying the boundary conditions, the macrodamage model parameters are calibrated. Validation against experimental tensile data confirms this approach's reliability. Furthermore, Nakajima tests reveal a discrepancy between the experimental forming limit curve and the one predicted by the modified maximum force criterion due to an early fracture before necking. This discrepancy is overcome through simulations incorporating the calibrated macrodamage model. The accuracy of predicting forming limits using finite element simulations is high. This framework offers a reliable, comprehensive approach for bridging microstructure and macroscale performance in DP steels, enhancing prediction accuracy for failure and formability across various materials.