  Additive manufacturing (AM) of metallic components promises many advantages
over conventional manufacturing processes through high design flexibility
across multiple length scales and precision coupled with an astonishing
combination of mechanical properties. Characterizing the relationship between
microstructure and mechanical properties remains one of the major challenges
for this novel technology. A natural precursor is identifying the influence of
the processing path on the developing microstructure. We combine experimental
studies of single-track laser powder bed fusion (LPBF) scans of AISI 316L
stainless steel, finite element analyses, and large-scale three-dimensional
discrete dislocation dynamics simulations to provide a unique understanding of
the underlying mechanisms leading to the formation of heterogeneous defect
structures in additively manufactured metals. Our results show that the
interruption of dislocation slip at solidification cell walls is responsible
for the formation of cellular dislocation structures, highlighting the
significance of solute segregation for plastic deformation of additively
manufactured components. This work provides a mechanistic perspective on
heterogeneous microstructure formation and opens the potential for a reliable
prediction of the resulting mechanical properties of additively manufactured
parts.
