On the constitutive relationship between solidification cells and the fatigue behaviour of IN718 fabricated by laser powder bed fusion

Alessandro Piglione*, Bonnie Attard, Vitor Vieira Rielli, Claudia Tatiana Santos Maldonado, Moataz M. Attallah, Sophie Primig, Minh Son Pham

*Corresponding author for this work

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Abstract

IN718 combines excellent mechanical properties with a good weldability and is therefore an ideal alloy for laser powder bed fusion (LPBF). Knowledge of the relationship between its as-built microstructure, particularly solidification cells, and its fatigue properties is needed to better utilise additively manufactured microstructures and guide their further optimisation. This study presents a comprehensive investigation of the as-built microstructure and the associated monotonic and fatigue properties of LPBF IN718 aimed at highlighting the influential effect of solidification cells on monotonic and cyclic plasticity. In monotonic tension, cells induced pronounced strain hardening and good ductility by acting as strong yet not impenetrable obstacles to dislocation slip. In fatigue loading, cyclic hardening followed by cyclic softening was linked to the stability of the as-built solidification cells, the high initial dislocation densities and the subsequent rearrangements of such dislocations during cyclic loading using the similitude relation and the evolution of friction and back stresses. By thoroughly investigating the evolution of the cyclic response of samples printed using two different scanning patterns, the relationship between process (scanning line length and thus local substrate temperature), microstructure (dislocation cell size and their spatial arrangement) and mechanical properties (cyclic hardening and softening responses) was comprehensively discussed.

Original languageEnglish
Article number102347
Number of pages19
JournalAdditive Manufacturing
Volume47
Early online date23 Sep 2021
DOIs
Publication statusPublished - Nov 2021

Bibliographical note

Funding Information:
A. Piglione and M.S.-Pham would like to thank the Beijing Institute of Aeronautical Materials (BIAM) for their support. Most characterisation studies in this work were performed at the BIAM-Imperial Centre for Materials Characterisation, Processing and Modelling at Imperial College London. The authors acknowledge the facilities, as well as the scientific and technical support of the Microscopy Australia node at The University of Sydney (Sydney Microscopy & Microanalysis). S. Primig is supported by the Australian Research Council DECRA ( DE180100440 ) and UNSW Scientia Fellowship schemes.

Publisher Copyright:
© 2021 Elsevier B.V.

Keywords

  • Cyclic plasticity
  • Fatigue
  • IN718
  • Laser powder bed fusion
  • Solidification cells

ASJC Scopus subject areas

  • Biomedical Engineering
  • Materials Science(all)
  • Engineering (miscellaneous)
  • Industrial and Manufacturing Engineering

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