Dislocation Distribution, Crystallographic Texture Evolution, and Plastic Inhomogeneity of Inconel 718 Fabricated by Laser Powder Bed Fusion
Jalal Al-Lami, Thibaut Dessolier, Samuel R. Rogers, Talha Pirzada, Minh‐Son Pham
Abstract
Plastic inhomogeneity, particularly localized strain, is one of the main mechanisms responsible for failures in engineering alloys. This work studies 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 results 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 results in an overall high density of geometrically necessary dislocations (GNDs) that are particularly dense in the fine grains. Although the Cube‐like texture desirable for isotropy is dominant, it gradually weakens during plastic deformation and the undesirable Goss‐like component (second most dominant in the as‐built microstructure) increases. The highly clustered and bimodal distribution of fine and coarse grains, textures, and GND densities causes fast localized roughening during deformation, particularly along the line row of fine Cube‐like grains. However, the chessboard strategy results 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 remains stable throughout plastic deformation. This results in more uniform deformation, reducing plastic inhomogeneity.