β Grain refinement by yttrium addition in Ti-6Al-4V Wire-Arc Additive Manufacturing

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dc.contributor.authorKennedy, Jacob R.
dc.contributor.authorDavis, Alec E.
dc.contributor.authorCaballero, Armando E.
dc.contributor.authorByres, N.
dc.contributor.authorWilliams, Stewart
dc.contributor.authorPickering, E. J.
dc.contributor.authorPrangnell, P. B.
dc.date.accessioned2022-02-07T15:44:23Z
dc.date.available2022-02-07T15:44:23Z
dc.date.issued2021-11-14
dc.description.abstractWire-Arc Additive Manufacturing (WAAM) of large near-net-shape titanium parts has the potential to reduce costs in aerospace applications. However, with titanium alloys, such as Ti-6Al-4V, conventional WAAM processing conditions generally result in epitaxial solidification from the melt pool fusion boundary, which over many layers can generate coarse cm-scale,<001>//ND fibre textured, columnar β grain structures within the deposited metal. The mechanical anisotropy caused by this coarse primary grain structure cannot be eliminated by subsequent solid-state phase transformations. In order to attempt to refine the size of the solidified β-grains and reduce their strong texture, the growth restriction efficiency of low addition levels of the strongly partitioning element (k = 0.1) yttrium (Y) has been investigated. Less than 0.8 wt.% Y was sufficient to reduce the widths of the solidified columnar β grains from 1 to 2 mm to 100–300 µm. Y was also found to induce a columnar-to-equiaxed transition (CET) in the latter stages of melt pool solidification, which benefits from a lower liquid thermal gradient and higher solidification velocity. Inter-dendritic segregation of Y was also found to be significant and oxygen scavenging led to the formation of Y2O3 particles in the inter-dendritic liquid, with a previously unreported irregular eutectic morphology. High-resolution EBSD analysis showed these particles exhibited specific orientation relationships with the solidified β grains, which were confirmed experimentally.en_UK
dc.identifier.citationKennedy JR, Davis AE, Caballero AE, et al., (2022) β grain refinement by yttrium addition in Ti-6Al-4V wire-arc additive manufacturing. Journal of Alloys and Compounds, Volume 895, Part 2, February 2022, Article number 162735en_UK
dc.identifier.issn0925-8388
dc.identifier.urihttps://doi.org/10.1016/j.jallcom.2021.162735
dc.identifier.urihttps://dspace.lib.cranfield.ac.uk/handle/1826/17550
dc.language.isoenen_UK
dc.publisherElsevieren_UK
dc.rightsAttribution-NonCommercial-NoDerivatives 4.0 International*
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/4.0/*
dc.subjectAdditive manufacturingen_UK
dc.subjectGrain refinementen_UK
dc.subjectTitaniumen_UK
dc.subjectTi64en_UK
dc.subjectWAAMen_UK
dc.titleβ Grain refinement by yttrium addition in Ti-6Al-4V Wire-Arc Additive Manufacturingen_UK
dc.typeArticleen_UK

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