Title: Influence of Crystal Orientation on the Freckle Formation in Directionally Solidified Superalloys
Authors: Ma, Dexin
Mathes, Michael
Zhou, Bin
Bührig-Polaczek, Andreas #
Issue Date: 4-Jul-2011
Publisher: Trans Tech Publications Ltd.
Host Document: Advanced Materials Research vol:278 pages:114-119
Conference: Euro Superalloys 2010
Abstract: Freckle occurrence is known to be dependent on the casting size and the superalloy
components with large cross section are more prone to freckle formation. In our directional
solidification experiment of superalloys freckles are observed in some thin samples, while some
significantly thicker samples in the same shell mould cluster remain freckle free. The EBSD
analysis shows that the samples with freckles have a good <001> axial orientation, while in freckle
free samples the primary dendrite stems diverge from the sample axis. In an analogue system the
flow behaviour through a mushy zone was simulated, in which the dendrite network was placed in
different orientation. The <001> dendrite array shows the lowest resistance to the vertical melt
flow. As the dendrite alignment diverges from <001> orientation, the flow speed slows down and
reaches the minimum at the <111> orientation. This orientation effect of the interdendritic
permeability explains well why the crystal orientation plays such an important role in the
occurrence of freckles in superalloy castings.
ISSN: 1022-6680
Publication status: published
KU Leuven publication type: IC
Appears in Collections:Non-KU Leuven Association publications
# (joint) last author

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