Criticality of porosity defects on the fatigue performance of wire + arc additive manufactured titanium alloy

Romali Biswal, Xiang Zhang, Abdul Syed, Mustafa Awd, Jialuo Ding, Frank Walther, Stewart Williams

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    65 Citations (Scopus)
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    Abstract

    This study was aimed at investigating the effect of internal porosity on the fatigue strength of wire + arc additive manufactured titanium alloy (WAAM Ti-6Al-4V). Unlike similar titanium alloys built by the powder bed fusion processes, WAAM Ti-6Al-4V seldom contains gas pores. However, feedstock may get contaminated that may cause pores of considerable size in the built materials. Two types of specimens were tested: (1) control group without porosity referred to as reference specimens; (2) designed porosity group using contaminated wires to build the specimen gauge section, referred to as porosity specimens. Test results have shown that static strength of the two groups was comparable, but the elongation in porosity group was reduced by 60% and its fatigue strength was 33% lower than the control group. The stress intensity factor range of the crack initiating pore calculated by Murakami’s approach has provided good correlation with the fatigue life. The kink point on the data fitting curve corresponds well with the threshold value of the stress intensity factor range found in the literature. For predicting the fatigue limit, a modified Kitagawa-Takahashi diagram was proposed consisting of three regions depending on porosity size. Critical pore diameter was found to be about 100 µm.
    Original languageEnglish
    Pages (from-to)208-217
    Number of pages10
    JournalInternational Journal of Fatigue
    Volume122
    Early online date28 Jan 2019
    DOIs
    Publication statusPublished - May 2019

    Bibliographical note

    NOTICE: this is the author’s version of a work that was accepted for publication in International Journal of Fatigue. 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 International Journal of Fatigue, [122], (2019] DOI: 10.1016/j.ijfatigue.2019.01.017

    © 2017, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

    Keywords

    • Additive manufacturing
    • Kitagawa-Takahashi diagram
    • Porosity defects
    • Stress intensity factor
    • Ti-6Al-4V

    ASJC Scopus subject areas

    • Modelling and Simulation
    • Materials Science(all)
    • Mechanics of Materials
    • Mechanical Engineering
    • Industrial and Manufacturing Engineering

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