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Flow effects on the fractal dimension of dendrites in an AlSiMg cast alloy

Genau, Amber and Ratke, Lorenz (2009) Flow effects on the fractal dimension of dendrites in an AlSiMg cast alloy. Euromat 2009, 7.-10. Sept. 2009, Glasgow, UK. (Unpublished)

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Abstract

The microstructure of directionally solidified AlSi7Mg0.6 alloys (A357) mainly consists of primary phase Al-dendrites in an AlSi eutectic matrix with some Mg2Si particles dilute in the interdendritic region. The dendritic network is conventionally characterized by measuring the primary dendrite spacing and the specific surface area on sections perpendicular to the growth direction, and the secondary arm spacing on longitudinal sections. These global measures of the dendrite network do not, however, adequately describe the branched appearance of secondary and tertiary arms. We therefore took up the idea of, for instance, Bilgram and co-workers to further characterize the microstructure by determining the fractal dimension of the primary phase dendrites. We used samples of A357 directionally solidified with a 3 K/mm temperature gradient and solidification velocities of 20 to 1200 µm/s. Samples were solidified with and without rotating magnetic fields (RMF), which induced a fluid flow of around 10 mm/s as a maximum velocity. Different methods were used to determine the fractal dimension on cross sections taken through the samples. A clear dependence of fractal dimension on solidification velocity is seen, while the effects of fluid flow are less apparent. We discuss our experimental observations with reference to the scarce literature data.

Document Type:Conference or Workshop Item (Poster)
Title:Flow effects on the fractal dimension of dendrites in an AlSiMg cast alloy
Authors:
AuthorsInstitution or Email of Authors
Genau, AmberUNSPECIFIED
Ratke, LorenzUNSPECIFIED
Date:September 2009
Status:Unpublished
Keywords:dendritic solidification, fractal structures, Al-alloys
Event Title:Euromat 2009
Event Location:Glasgow, UK
Event Type:international Conference
Event Dates:7.-10. Sept. 2009
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W FR - Forschung unter Weltraumbedingungen (old)
DLR - Research area:Space
DLR - Program:W FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):W - Vorhaben Materialwissenschaftliche Forschung (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Physics in Space
Deposited By: Prof. Lorenz Ratke
Deposited On:10 Nov 2009 08:42
Last Modified:10 Nov 2009 08:42

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