New mechanistic insights of dislocation configurations in strain hardening of additively manufactured 316 L stainless steel

Laser powder bed fusion ( L -PBF) offers a promising pathway toward achieving the long-sought strength-ductility synergy, widely attributed to the formation of self-organized cellular dislocation structures. However, the mechanistic roles of dislocation-related interfacial features in mediating strain hardening and ductility remain insufficiently understood. In this study, we systematically investigate the distinct mechanical contributions of chemical segregation-decorated dislocation cell (CS-DC) boundaries and dislocation-woven low-angle grain (DW-LAG) boundaries in L -PBF 316 L stainless steel. Compared to CS-DC boundaries, DW-LAG boundaries substantially enhance strain-hardening capability, enabling exceptional ductility (uniform elongation ∼68%) and comparable tensile strength. This finding suggests the critical role of DW-LAG boundaries to post-yield deformation behavior and supports a reassessment of the relative contributions of these interfacial features in L -PBF alloys. Furthermore, dislocation micro-behaviors and hetero-deformation induced (HDI) stresses at various strains were quasi-in-situ tracked via multiscale characterization techniques. In contrast to the soft barriers posed by CS-DC boundaries, DW-LAG boundaries function as modulators that block dislocations, facilitating the accumulation of geometrically necessary dislocations at internal interfaces, thereby contributing to sustainable strain hardening. This work revisits the micro-mechanisms of dislocation configurations on the strain hardening behavior of L -PBF alloys, offering new insights into targeted design optimization for advanced additively manufactured metals.