Selective Laser Melting of 316L Stainless Steel: Physics of Melting Mode Transition and Its Influence on Microstructural and Mechanical Behavior
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A combined computational–experimental study is performed to investigate the effect of melting modes (conduction, transition and keyhole) on 316L stainless steel parts fabricated by selective laser melting. A high-fidelity mesoscale model is developed using the LIGGGHTS and OpenFOAM open-source codes to describe the physical phenomena (convection, melting, evaporation and solidification), melt flow dynamics and melting mode transition. The developed model helps to understand laser/matter interaction, melting of particles, the effect of recoil pressure and the formation of fusion zone. The computational results were found consistent with the single-track experimental results. Furthermore, for establishing the influence of melting mode on microstructural and mechanical properties, bulk samples with different melting modes were fabricated and characterized by comparing the microstructure, microhardness, nanohardness and tensile behavior. The experimental results showed that the stable keyhole mode results in higher hardness, higher elongation and finer cellular grains compared with the conduction mode.