Fatigue crack propagation behaviour in wire+arc additive manufactured Ti‐6Al‐4V: Effects of microstructure and residual stress

J. Zhang, X. Wang, S. Paddea, X. Zhang

Research output: Contribution to journalArticle

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Abstract

Fatigue crack propagation tests of Ti‐6Al‐4V fabricated by the Wire+Arc Additive Manufacturing (WAAM) process are analysed. Crack growth rate and trajectory are examined before and after the crack tip crossing an interface between the WAAM and wrought alloys. The study has focused on the microstructure and residual stress effect. First, the differences in crack growth rate and path between WAAM and wrought alloys are attributed to their different microstructure; the equiaxed wrought alloy has straight crack path, whereas the WAAM lamellar structure causes tortuous crack path resulting in lower crack growth rate. Second, based on measured residual stress profile in the as-built WAAM piece, retained residual stress in the much smaller compact tension specimens and its effect on crack growth rate are calculated by the finite element method. Numerical simulation shows considerable residual stress in the test specimen and the stress magnitude depends on the initial crack location and propagation direction in relation to the WAAM-wrought interface. Residual stress is released immediately if the initial crack is in the wrought substrate; hence it has little effect. In contrast, when crack grows from WAAM to wrought, residual stress is retained resulting in higher stress intensity factor; hence greater crack growth rate.

Original languageEnglish
Pages (from-to)551-561
JournalMaterials and Design
Volume90
DOIs
Publication statusPublished - 2016

Fingerprint

3D printers
Fatigue crack propagation
Residual stresses
Wire
Microstructure
Crack propagation
Cracks
Lamellar structures
titanium alloy (TiAl6V4)
Stress intensity factors
Crack tips
Trajectories
Finite element method

Bibliographical note

NOTICE: this is the author’s version of a work that was accepted for publication in Materials and Design. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in [Materials and Design, [90 (2016)] DOI: 10.1016/j.matdes.2015.10.141

© 2016, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

Keywords

  • Additive manufacturing
  • Titanium alloy
  • Fatigue crack propagation
  • Residual stress
  • Microstructure

Cite this

Fatigue crack propagation behaviour in wire+arc additive manufactured Ti‐6Al‐4V: Effects of microstructure and residual stress. / Zhang, J.; Wang, X.; Paddea, S.; Zhang, X.

In: Materials and Design, Vol. 90, 2016, p. 551-561.

Research output: Contribution to journalArticle

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