Achieving a columnar-to-equiaxed transition through dendrite twinning in high deposition rate additively manufactured titanium alloys

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dc.contributor.authorDavis, A. E.
dc.contributor.authorWainwright, J.
dc.contributor.authorSahu, V. K.
dc.contributor.authorDreelan, D.
dc.contributor.authorChen, Xin
dc.contributor.authorDing, Jialuo
dc.contributor.authorFlint, T.
dc.contributor.authorWilliams, Stewart
dc.contributor.authorPrangnell, P. B.
dc.date.accessioned2024-05-02T09:30:50Z
dc.date.available2024-05-02T09:30:50Z
dc.date.issued2024-04-09
dc.description.abstractThe coarse β-grain structures typically found in titanium alloys like Ti–6Al–4V (wt pct, Ti64) and Ti–6Al–2Sn–4Zr–2Mo–0.1Si (Ti6242), produced by high deposition rate additive manufacturing (AM) processes, are detrimental to mechanical performance. Certain modified processing conditions have been shown to lead to a more refined grain structure, which has generally been attributed to a change in the solidification conditions with respect to the experimental Hunt diagram proposed by Semiatin and Kobryn. It is shown that with Wire Arc AM (WAAM) increasing the wire feed speed (WFS) is effective in promoting a columnar-equiaxed transition (CET). Conversely, estimates of the dendrite-tip undercooling using the KGT model suggest that this will be too small for free nucleation without the addition of artificial nucleants, due to the very low solute partitioning in Ti alloys. It is also shown that it is difficult to promote a CET with plasma transferred arc WAAM as computational fluid dynamics (CFD) melt-pool simulations indicate that the solidification parameters remain within the columnar region on the Semiatin-Kobryn Hunt map, within the constraints of a stable process. However, a high fraction of twin boundaries was observed in the refined β-grain structures seen at high WFS. This has been attributed to departure of {001}β alignment from the direction of maximum thermal gradient, caused by the curvature of the fusion boundary, stimulating dendrite twinning during solidification. In addition, it is shown that increasing the WFS leads to a change in melt-pool geometry and a reduction of remelt depth, which promoted dendrite twinning and grain refinement.en_UK
dc.description.sponsorshipThe authors are appreciative of the EPSRC program grants NEWAM (EP/R027218/1) and LightForm (EP/R001715/1), for supporting aspects of this research. The authors acknowledge the use of equipment associated with the Advanced Metals Processing and Characterization themes of the Henry Royce Institute for Advanced Materials, funded through EPSRC grants EP/R00661X/1, EP/S019367/1, EP/P025021/1, and EP/P025498/1. P.B. Prangnell is grateful to the Royal Academy of Engineering, UK, and Airbus for supporting his research through the Airbus-University of Manchester Centre for Metallurgical Excellence.en_UK
dc.identifier.citationDavis AE, Wainwright J, Sahu VK, et al., (2024) Achieving a columnar-to-equiaxed transition through dendrite twinning in high deposition rate additively manufactured titanium alloys. Metallurgical and Materials Transactions A, Volume 55, June 2024, pp. 1765-1787en_UK
dc.identifier.eissn1543-1940
dc.identifier.issn1073-5623
dc.identifier.urihttps://doi.org/10.1007/s11661-024-07388-7
dc.identifier.urihttps://dspace.lib.cranfield.ac.uk/handle/1826/21304
dc.language.isoen_UKen_UK
dc.publisherSpringeren_UK
dc.rightsAttribution 4.0 International*
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/*
dc.titleAchieving a columnar-to-equiaxed transition through dendrite twinning in high deposition rate additively manufactured titanium alloysen_UK
dc.typeArticleen_UK
dcterms.dateAccepted2024-03-10

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