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The deformation behavior and strengthening mechanism of Inconel 718 with a hierarchical structure composed of microscale crystallographic lamellar microstructure (CLM) and nanoscale cellular structure, fabricated by laser powder bed fusion, were clarified via nanoscale microstructural and in-situ neutron diffraction analyses. The CLM is a layered structure parallel to the building direction (BD) and consists of relatively wide main and narrow sub-layers with 〈110〉 and 〈100〉 orientations, respectively, with respect to BD. This is the first study to demonstrate that the yield stress of the alloys depends strongly on deformation stresses of the sub-layers, even though Schmid factors of the primary slip system for both layers are the same. The sub-layer continues to deform elastically even beyond the micro-yield point of the main layer, which results in the macroscopic strengthening at an early stage of deformation. On the other hand, the cellular structure is formed in both layers, associated with a dendritic cell growth along 〈100〉 direction, Nb segregation between the cells and an accumulation of dislocations to decrease a residual stress. The cell boundaries with numerous dislocations and Nb segregation act as a strong barrier to dislocation motion resulting in a stress increase through the Hall-Petch law, even though they are low-angle grain boundaries. The spacing and morphology of the cell boundary depend strongly on fabrication conditions. The optimized cellular structure provides significant strengthening comparable to or greater than that caused by large-angle grain boundaries, thereby increasing the macroscopic strength of the alloys through hardening of the sub-layer.

Rights:

• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

  Published by Elsevier Inc. on behalf of Acta Materialia Inc. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ).

Keyword: Additive manufacturing, Nickel superalloys, Crystallographic texture, Cellular structure, Strengthening mechanism, Neutron diffraction

Date published: 2025-11-02

Publisher: Elsevier BV

Journal:

• Acta Materialia (ISSN: 13596454) vol. 303 p. 121696-121696 121696

Funding:

• Japan Society for the Promotion of Science 21H05196 (Grant-in-Aid for Transformative Research Area (A))
• Japan Proton Accelerator Research Complex 2022B0149
• Japan Science and Technology Agency JPMJCR2194 (CREST-Nanomechanics: Elucidation of macroscale mechanical properties based on understanding nanoscale dynamics of innovative mechanical materials)

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1016/j.actamat.2025.121696

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Updated at: 2026-01-05 14:55:20 +0900

Published on MDR: 2026-01-06 08:19:18 +0900