Multiscale crystal plasticity modeling of multiphase advanced high strength steel

Abstract

Designing multiphase metals based on their constituent phase micromechanical properties and using these metals for manufacturing lightweight automotive parts are a challenging process. A multiphase and multiscale model is strongly beneficial in achieving this goal, as such a model can play an important role in connecting the material response at the macroscopic scale with the microstructural properties. In the present study, a computationally efficient rate independent crystal plasticity finite element (CPFE) model was used to simulate the bulging test of a three-phase (ferrite, martensite, and retained austenite) quenched and partitioned Q&P980 advanced high strength steel (AHSS) sheet. The CPFE model was developed to capture the mechanical properties of the steel phases based on their individual plastic deformation and slip systems. The macroscopic behavior of the polycrystalline aggregate was then predicted based on the volume averaged response of the representative phases, and their volume fraction in the steel sheet. In addition to random texture distribution assumption for each grain, two methods were considered in this study for the initial volume fraction distribution of the phases in steel sheet to introduce the effect of inhomogeneity based on phase distributions. The objective of developing the proposed model is to investigate the material behavior of the AHSS from the uniaxial microscale tension tests to large deformation applications through validation with the macroscale deformation based on the bulge test. The comparison between the multiphase CPFE model, experiments, and two phenomenological models (isotropic von Mises and anisotropic Hill’48 yield criteria) was conducted for validation of the proposed model. Also, the numerical results were further evaluated by comparing the predicted against experimental forming limit curve (FLC). The results showed that the trend of the forming limit curve predicted by the multiphase CPFE model is in good agreement with experimental results.