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A comparative in situ X-radiography and DNN model study of solidification characteristics of an equiaxed dendritic Al-Ge alloy sample

Becker, Maike and Sturz, Laszlo and Bräuer, Dirk and Kargl, Florian (2020) A comparative in situ X-radiography and DNN model study of solidification characteristics of an equiaxed dendritic Al-Ge alloy sample. Acta Materialia, 201, pp. 286-302. Elsevier. doi: 10.1016/j.actamat.2020.09.078. ISSN 1359-6454.

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Abstract

In situ X-radiography imaging during the isothermal solidification of a 200 µm thin Al-24 at.% Ge sample was performed to determine dendritic growth rates, liquid concentrations and projected solid fractions. The experimental data allowed to follow dendrite tip growth velocities with high accuracy all the way from the initial transient growth related decrease of velocity via the expected increase of velocity during free dendrite growth to its final decrease during neighbor interacted growth. Concentration profiles in front of individual dendrite tips were measured to analyze the increase in far-field solute concentration due to solute accumulation. By time-resolved imaging of almost the entire 12 mm diameter sample, the global melt concentration could be derived. This enabled to estimate the initial nucleation undercooling of this un-refined alloy, which was so far unresolved. The experimental results are compared to a three-dimensional dendrite needle network model that simulates the experimental conditions, such as hexagonal dendrite structures and confined sample geometry. Although the simulation results are very sensitive to variations of the parameters undercooling and dendrite selection constant, one model parameter set is found that reproduces all experimentally measured solidification characteristics. The thorough experiment-model comparison indicates that the dendritic growth rates in this experimental configuration can be lower by a factor of 7 depending on undercooling than in the non-confined case.

Item URL in elib:https://elib.dlr.de/136709/
Document Type:Article
Title:A comparative in situ X-radiography and DNN model study of solidification characteristics of an equiaxed dendritic Al-Ge alloy sample
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Becker, MaikeMaike.Becker (at) dlr.dehttps://orcid.org/0000-0002-6732-5411
Sturz, Laszlol.sturz (at) access-technology.deUNSPECIFIED
Bräuer, Dirkdirk.braeuer (at) dlr.deUNSPECIFIED
Kargl, FlorianFlorian.Kargl (at) dlr.deUNSPECIFIED
Date:December 2020
Journal or Publication Title:Acta Materialia
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:201
DOI :10.1016/j.actamat.2020.09.078
Page Range:pp. 286-302
Publisher:Elsevier
ISSN:1359-6454
Status:Published
Keywords:Röntgenradiographie, Al-Ge-Legierung, Echtzeit-Erstarrung, dendritisches Wachstum, Simulation
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 - Materials Research and Microgravity (MuM)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Physics in Space
Deposited By: Becker, Maike
Deposited On:02 Nov 2020 13:50
Last Modified:02 Nov 2020 13:50

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