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Dendrite Orientation Transition in Al-Ge Alloys

Becker, Maike and Dantzig, John and Kolbe, Matthias and Wiese, Sebastian Thomas and Kargl, Florian (2018) Dendrite Orientation Transition in Al-Ge Alloys. Acta Materialia, 165, pp. 666-677. Elsevier. doi: https://doi.org/10.1016/j.actamat.2018.12.001. ISSN 1359-6454.

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Official URL: https://www.sciencedirect.com/science/article/abs/pii/S1359645418309431#!


We report on a dendrite orientation transition (DOT) discovered in the Al-Ge system by conducting isothermal solidification experiments in thin samples under slow cooling conditions. The DOT was revealed using a combination of in situ X-radiography imaging and post-mortem electron backscatter diffraction. In Al-20 wt% Ge the primary arms grow along <100>, whereas in Al-46 wt% Ge the primary arms grow along <110>. At an intermediate composition of Al-29 wt% Ge, we observe both directions growing simultaneously. Phase-field simulations in which the solid-liquid interfacial energy anisotropy was systematically varied to correspond with the composition changes reproduced the experimentally observed microstructures. The remarkable agreement between the experimental observations and the simulations provides strong evidence that the DOT in this alloy system is caused by modification of surface energy anisotropy with increasing Ge content. Furthermore, we show that the confinement due to the thin sample geometry influences the selection of the primary growth directions, so that different growth morphologies develop depending on the orientation of the crystal in the sample.

Item URL in elib:https://elib.dlr.de/124889/
Document Type:Article
Title:Dendrite Orientation Transition in Al-Ge Alloys
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Becker, MaikeMaike.Becker (at) dlr.deUNSPECIFIED
Dantzig, Johndantzig (at) illinois.eduUNSPECIFIED
Kolbe, Matthiasmatthias.kolbe (at) dlr.deUNSPECIFIED
Wiese, Sebastian Thomassebastian.wiese (at) rwth-aachen.deUNSPECIFIED
Kargl, Florianflorian.kargl (at) dlr.deUNSPECIFIED
Date:5 December 2018
Journal or Publication Title:Acta Materialia
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :https://doi.org/10.1016/j.actamat.2018.12.001
Page Range:pp. 666-677
Keywords:dendritic growth X-radiography phase-field modeling surface energy anisotropy
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Research under Space Conditions
DLR - Research theme (Project):R - Material Design and New Materials, R - Materials Research and Microgravity (MuM)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Physics in Space > Scientific Experiments MP
Deposited By: Kargl, Dr Florian
Deposited On:13 Dec 2018 12:51
Last Modified:07 Jan 2019 08:01

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