Dislocation Distribution, Crystallographic Texture Evolution, and Plastic Inhomogeneity of Inconel 718 Fabricated by Laser Powder Bed Fusion

Abstract

Plastic inhomogeneity, particularly localised strain, is one of the main mechanisms responsible for failures in engineering alloys. This work studied the spatial arrangement and distribution of microstructure (including dislocations and grains) and their influence in the plastic inhomogeneity of Inconel 718 fabricated by additive manufacturing (AM). The bidirectional scanning strategy with no interlayer rotation resulted in highly ordered alternating arrangements of coarse Goss‐like {110}<001> textured grains separated by fine Cube‐like {100}<001> textured grains. The bidirectional strategy also resulted in an overall high density of geometrically necessary dislocations (GNDs) that were particularly dense in the fine grains. Although the Cube‐like texture desirable for isotropy was dominant, it gradually weakened during plastic deformation and the undesirable Goss‐like component (second most dominant in the as‐built microstructure) increased. The highly clustered and bimodal distribution of fine and coarse grains, textures and GND densities caused fast localised roughening during deformation, particularly along the line row of fine Cube‐like grains. However, the chessboard strategy resulted in a lower GND density and a comparatively more random distribution of crystallographic texture and GNDs, with a dominant Cube‐like component (and much lower Goss‐like texture) that remained stable throughout plastic deformation. This resulted in more uniform deformation, reducing plastic inhomogeneity.This article is protected by copyright. All rights reserved.