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Synchrotron tomographic quantification of the influence of Zn concentration on dendritic growth in Mg-Zn alloys

Shuai, S; Guo, E; Wang, J; Phillion, AB; Jing, T; Ren, Z; Lee, PD; (2018) Synchrotron tomographic quantification of the influence of Zn concentration on dendritic growth in Mg-Zn alloys. Acta Materialia , 156 pp. 287-296. 10.1016/j.actamat.2018.06.026. Green open access

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Abstract

Dendritic microstructural evolution during the solidification of Mg-Zn alloys was investigated as a function of Zn concentration using in situ synchrotron X-ray tomography. We reveal that increasing Zn content from 25 wt% to 50 wt% causes a Dendrite Orientation Transition (DOT) from a six-fold snow-flake structure to a hyper-branched morphology and then back to a six-fold structure. This transition was attributed to changes in the anisotropy of the solid-liquid interfacial energy caused by the increase in Zn concentration. Further, doublon, triplon and quadruplon tip splitting mechanisms were shown to be active in the Mg-38 wt%Zn alloy, creating a hyper-branched structure. Using the synchrotron tomography datasets, we quantify, for the first time, the evolution of grain structures during the solidification of these alloys, including dendrite tip velocity in the mushy zone, solid fraction, and specific surface area. The results are also compared to existing models. The results demonstrate the complexity in dendritic pattern formation in hcp systems, providing critical input data for the microstructural models used for integrated computational materials engineering of Mg alloys.

Type: Article
Title: Synchrotron tomographic quantification of the influence of Zn concentration on dendritic growth in Mg-Zn alloys
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.actamat.2018.06.026
Publisher version: https://doi.org/10.1016/j.actamat.2018.06.026
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. - Please note: a corrigendum to this paper was issued on 15/11/18 (https://doi.org/10.1016/j.actamat.2018.11.006).
Keywords: Magnesium alloys, Zinc, 4D imaging, Dendrite orientation transition, Morphology transition
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/10053479
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