Evolution of dislocation cellular pattern in Inconel 718 alloy fabricated by laser powder-bed fusion

Abstract

The dislocation cellular pattern (DCP) is a predominant microstructure in laser-based additively manufactured metals. Understanding the evolution of DCP paves the way for optimizing the laser-produced microstructure, which can ultimately modify the mechanical properties. In this work, we combined tensile test and multiscale characterization methods to systematically study the development of DCP in deformed Inconel 718 alloy that was processed with laser powder-bed fusion technique. Although the DCP has a similar appearance as the deformation-induced dislocation cell, the wall of DCP consists of solute atoms and small precipitates, which are absent in the conventional dislocation cell. The development of DCP during plastic deformation was independent of crystal orientation. The evolution process of DCP can be divided into two stages. At a tensile strain lower than 10%, the size of DCP was independent of flow stress. At higher strain levels, the DCP size decreased; however, the maximum reduction obtained at the strain-to-failure was only ~27% of the undeformed DCP size. The geometrically necessary dislocation density at DCP boundaries increased as increasing strain. Because of the interactions of dislocation tangles, solute atoms, and precipitates in the DCP wall, the DCP configuration is stabilized, and its role in deformation was neither like that of the dislocation cell nor that of the grain boundary.