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Morphological characterization of the directionally solidified AlAgCu ternary eutectic

Genau, Amber and Ratke, Lorenz (2009) Morphological characterization of the directionally solidified AlAgCu ternary eutectic. Euromat 2009, 7.-10. Sept. 2009, Glasgow, UK. (Unpublished)

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Abstract

Ternary eutectic microstructures have a level of complexity far exceeding that of binary eutectics. While developing from the liquid, three phases are attempting to minimize the interfacial areas and the diffusion distances between them, and thus they cannot develop simple structures like lamellae or fibres as are often observed in nf-nf eutectics such as AlCu or AgCu. In sections taken perpendicular to the growth direction, microstructures have been observed with various morphologies, including a highly organized structure which resembles stacked bricks. There is no detailed description of ternary eutectic structures in the literature and only a limited model made by Himemiya available that extends the classical Jackson and Hunt theory to simple geometrical arrangements of ternary eutectics. We therefore performed directional solidification experiments with the ternary eutectic AlCuAg alloy. The temperature gradient ahead of the eutectic interface was kept constant at 3 K/mm and the solidification velocity varied from 0.2 to 5 µm/s. The microstructures observed contain an Al-rich phase and the Al2Cu and Ag2Al phases with nontrivial shapes. We analyze in cross section the distance distributions between the phases, the distribution of interphase separations, the volume fraction and surface area of all phases and determine correlation functions. The variation of these parameters with solidification velocity, along with further experimental observations and analyses, will be discussed with respect to eutectic growth theory.

Document Type:Conference or Workshop Item (Speech)
Title:Morphological characterization of the directionally solidified AlAgCu ternary eutectic
Authors:
AuthorsInstitution or Email of Authors
Genau, AmberUNSPECIFIED
Ratke, LorenzUNSPECIFIED
Date:September 2009
Status:Unpublished
Keywords:ternary alloys, eutectic solidification, microstructural characterisation, morphology
Event Title:Euromat 2009
Event Location:Glasgow, UK
Event Type:international Conference
Event Dates:7.-10. Sept. 2009
Organizer:FEMS
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 08:43
Last Modified:10 Nov 2009 08:43

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