Determination of Critical Microstructural Features in an Austenitic Stainless Steel Using Image-Based Finite Element Modeling

Two-dimensional (2-D) and three-dimensional (3-D) image-based finite element (FE) modeling and scientific visualization techniques were employed to determine the critical microstructural features that control mechanical behavior in a commercial austenitic stainless steel, AL-6XN. Two-dimensional FE meshes were generated using microstructural images obtained from electron backscatter diffraction (EBSD), and three-dimensional meshes were generated from microstructural reconstructions created using serial-sectioning techniques and EBSD. Image-based FE simulations were run using anisotropic elasticity. The 2-D simulations revealed that higher local elastic stresses are produced near grain boundaries than at grain interiors for various loading conditions. Under normal uniaxial loading conditions, higher stresses were observed at faceted grain boundaries, particularly those with a Σ = 3 coincident site lattice misorientation. Under simple shear loading conditions, however, the highest stresses were observed at general high-angle grain boundaries. In the 3-D simulations, similar relationships held, with the highest elastic stresses observed at the junction between two Σ3 boundaries under normal uniaxial loading and slightly lower elastic stresses at these junctions under simple shear loading. In the 3-D models, high elastic stresses were associated only with grain boundaries and triple junctions and showed little to no correlation with grain size or morphology.