A comparison of dislocation cellular patterns generated in Inconel 718 alloy and pure Ni fabricated by laser powder bed fusion

Abstract

The dislocation cellular pattern (DCP) plays an important role on the mechanical property of metals fabricated by laser powder bed fusion technique. Understanding the origin and evolution of the DCP is of critical importance to the selection of manufacturing parameters. However, the generation mechanism of DCP is not clear. By using multiscale characterization approaches, we investigated and compared the DCP in Inconel 718 alloy and pure Ni fabricated by laser powder bed fusion technique. In Inconel 718, the dislocations tended to multiply and be pinned along the solidified cellular dendrites boundaries. As the solidified cellular dendrites had a preferential growth direction of <001>, the DCP inherited this orientation and exhibited a three-dimensional rod-like shape. In contrast, the DCP in pure Ni was the same as the conventional dislocation cell generated by plastic deformation. Without constriction from solute atoms and precipitates, the DCP in Ni tended to recover and form low-angle grain boundaries. Our results suggested that the thermal stress induced by rapid heating/cooling during laser fabrication played a critical role on the generation of high-density dislocations, and the solute atoms influenced the geometry and morphology of the DCP.