The interplay of local chemistry and plasticity in controlling microstructure formation during laser powder bed fusion of metals

TL;DR

This paper investigates how local chemistry and plasticity influence microstructure formation during laser powder bed fusion of metals, combining experiments, finite element analysis, and dislocation simulations to understand defect structures.

Contribution

It introduces a mechanistic understanding of microstructure formation in metal additive manufacturing, emphasizing the role of solute segregation and dislocation behavior.

Findings

Dislocation slip interruption at solidification cell walls causes cellular dislocation structures.

Solute segregation significantly affects plastic deformation in additively manufactured metals.

The study offers a pathway to predict mechanical properties based on microstructure formation mechanisms.

Abstract

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.