Understanding orientation-dependent plasticity in laser beam powder bed fusion stainless steel through crystal plasticity modelling

Single-crystal-like stainless steel 316L (SS316L) was tailored by laser beam powder bed fusion (PBF-LB). Tensile responses along the <100>, <110> and <111> crystallographic directions show considerably different strength ratios in different orientations from a standard face-centered cubic (FCC) alloy. A multi-scale crystal plasticity modelling methodology is developed to simulate and understand such unique orientation-dependent plastic deformation behaviour. The polycrystal model, based on the visco-plastic self-consistent (VPSC) formulation, considers deformation by slip and twinning, adapting a dislocation-based approach with latent hardening at single crystal level, including slip-slip, slip-twin, twin-slip and twin-twin interactions, to account for the orientation-dependent strain hardening behaviour. Based on the proposed multi-scale model, the orientation-dependent superior strength-ductility behaviour of textured PBF-LB SS316L can be attributed to the beneficial effects of deformation twinning and the cellular sub-grain structure.