Metallurgically-driven thermomechanical analysis of multiple side-to-side laser melting on a 316L substrate

In additive manufacturing, the solidification grain structure has a significant influence on the properties of as-built material. In this context, the solidification grain structure and internal stress evolution during laser scanning of polycrystalline 316L stainless steel are simulated. A strongly coupled crystal viscoplasticity model is developed and integrated with a cellular automaton–finite element (CAFE) approach to accurately capture grain structure and stress evolution, where the CAFE model is validated based on a literature experiment. The crystal viscoplasticity model is calibrated using stress–strain curves of annealed 316L from experiments considering small thermo-elasto-viscoplastic (TEVP) deformations. The resolution algorithm dynamically couples heat transfer, melting and solidification simulations while concurrently computing stress and strain evolution within the grain structure. Four scanning strategies are simulated using the coupled CAFE–crystal viscoplasticity approach, capturing stress evolution during grain growth. This enables the simultaneous thermo-viscoplastic modeling in the mushy zone and TEVP modeling in the solid, providing insights into stress evolution and grain orientation over a large domain. The melting-solidification process involves variations in compression and tension, leading to stress concentration within neighboring grains with significant orientation differences, extending along elongated grains. A framework for multiscale process-structure-mechanical investigation is established based on microscale stress evolution in additive manufacturing.