A micro mechanical study on tensile behavior of steel sheets with spheroidal cementite using crystal plasticity finite element method

Abstract

In this research, we investigate the effects of various microstructural features on the behavior of spherical steel sheets, using the crystal plasticity finite element method. The cementite phase ratio, the grain sizes of ferrite and cementite, and the percentage of residual pearlite in the steel structure due to incomplete annealing are the major microstructural parameters studied in this work. A grain generator software has been developed to generate hexagonal ferrite grains as well as circular cementite particles distributed in the ferrite matrix. We use a hard coating with special properties as an intermediate layer around the cementite grains to simulate the contact between ferrite grains and cementite particles. This software can also assist with the preprocessing including boundary condition and load producing and introducing constitutive modeling relations. We use representative volume elements (RVEs) to simulate the microstructure of the steel sheet. The hardening parameters in the simulations are calibrated according to the available experimental data in the literature. Several RVEs were prepared and solved to investigate the effect of the thickness of this layer on material behavior. We can replicate the experimental results by setting the ratio of this thickness to the cementite particles’ diameter to be 0.25. Moreover, by reducing the size of ferrite grains and cementite particles, the strength of steel increases. On the other hand, increasing the ratio of the cementite phase increases the strength of steel but the uniform plastic deformation of the material is reduced. We also model and discuss the remaining pearlite content and its effect on the flow behavior of the material. Finally, the effect of the cementite precipitation location and its bimodal size distribution were discussed in this study.