Anisotropic polycrystal plasticity due to microstructural heterogeneity: A multi-scale experimental and numerical study on additively manufactured metallic materials

Abstract

Additively manufactured (AM) metallic parts exhibit substantially different microstructures compared to those that are conventionally produced. Characterization studies have revealed that the microstructure of as-built AM metallic materials is highly heterogeneous in many respects. The strongly anisotropic mechanical response under plastic deformation observed in AM metals, compared to their conventionally manufactured counterparts, lies in the aforementioned inherent microstructural disparities. In this study, we have focused on a high-manganese steel (HMnS) processed by laser powder bed fusion (LPBF), which exhibits twinning-induced plasticity (TWIP). The as-built microstructure is carefully characterized by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. To unfold the potential of metal additive manufacturing, it is essential to understand the microstructure of AM products and its connection with the mechanical properties by means of numerical modeling and simulation. The mechanical response of AM components under plastic deformation is highly complex and its simulation requires advanced modeling and numerical methods. In the present study, in order to simulate the anisotropic plasticity of the LPBF-HMnS, we used the full field method for computational polycrystal homogenization combined with physics-based crystal plasticity constitutive and statistical microstructure modeling. The impact of different process-induced microstructural heterogeneity characteristics on macroscopic strain hardening behavior of the material has been comprehensively and systematically investigated. Finally, it has been argued why the chosen AM material with the selected processing parameters and chemical composition represented an ideal candidate for a generic assessment of the anisotropic polycrystal plasticity due to microstructural heterogeneity.