Microstructure Evolution and Deformation Mechanisms in Additively Manufactured 316L Stainless Steel

We investigate the evolution of deformation mechanisms and dislocation structures in 316L stainless steel produced by directed energy deposition (DED) across different strain levels. We show that the deformation mechanisms are strongly influenced by the initial dual-scale cellular structure. At low to moderate strains, plasticity is accommodated primarily by dislocation slip within the cell interiors and the formation of micro-bands. At higher strains, plastic deformation is primarily controlled by mechanical nano-twinning initiated through the overlap of stacking fault ribbons. Unlike conventionally processed 316L, the additively manufactured alloy exhibits an almost linear increase in dislocation density throughout the full range of plastic deformation. The retained cellular architecture impedes dislocation motion, contributing to the material’s high ductility. Finally, a clear correlation between work-hardening rate and deformation modes confirms the atypical plastic behavior of AM 316L, providing valuable insights for the development of large-scale predictive plasticity models for these steels.