Analyzing the cementite particle size and distribution in heterogeneous microstructure of C45EC steel using crystal plasticity based DAMASK code

The influence of microstructural attributes of crystalline material on its overall mechanical properties is of vital importance to get the desired plasticity of a component. Varying grain morphology and distribution of the multi-phase steels can pose plastic flow challenges during cold forming. The spheroidized medium carbon steels obtained by reforming the lamellar structured hard cementite particle networks present in alternating layers with soft ferrite phase in pearlite have remarkable microstructure with an overall better combination of ductility and strength. The spherical shaped cementite particles in spheroidized mild steel are responsible for heterogeneous material response at the local level during deformation due to their hard and strong nature. It eventually alters the overall mechanical behavior due to their size and distribution in the soft ferrite matrix. It is, therefore, necessary to precisely predict the mechanical response of the material by numerical simulations using microstructural models and crystal plasticity code. In this research study, Voronoi Tessellation based customized algorithms in Dream.3D are used to make microstructural models of spheroidized medium carbon steel. Crystal plasticity based constitutive mathematical material model is evaluated on continuum mechanics principles using DAMASK code. Representative Volume Elements (RVEs) with cementite particles spread 50% on the ferrite grain boundaries are first ensured to be grid-independent. RVEs of three cases with varying ferrite grain size, i.e., small, large, and bimodal, are simulated under tensile loading up to 30% of global strain. Local stress and strain maps of the RVEs are critically analyzed. The changing effect of the cementite grain size and distribution within the ductile ferrite phase on local material behavior is observed. Stress localization is observed on the bases of the distribution of cementite phase particles and quantitatively presented. The information can be used to better design the thermo-mechanical processing of the mild steel sheets and rods to get a better mechanical response during plastic deformation in cold forming processes such as in the automotive industry.