Origin of Equiaxed Grains and their Motion in the Liquid Phase

In order to investigate the multiplication of equiaxed grains by the forced convection, in-situ observation using a transparent organic substance have been made. The emission of some spherical particles from the columnar zone was observed by a fiber scope installed in an ingot case. These particles...

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Bibliographic Details
Published in:ISIJ International 2003/09/15, Vol.43(9), pp.1415-1420
Main Authors: Esaka, Hisao, Wakabayashi, Tomokazu, Shinozuka, Kei, Tamura, Manabu
Format: Article
Language:English
Subjects:
Applied sciences
columnar dendrite
equiaxed grain
Exact sciences and technology
Metallurgical fundamentals
Metals. Metallurgy
multiplication
natural convection
Production of metals
secondary dendrite arm
solidification
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Summary:In order to investigate the multiplication of equiaxed grains by the forced convection, in-situ observation using a transparent organic substance have been made. The emission of some spherical particles from the columnar zone was observed by a fiber scope installed in an ingot case. These particles are originally the secondary dendrite arms and are detached by the fluctuations of thermal and/or solutal fields and/or mechanical breaking. Then the particles fell down in the liquid along with the natural convection. This event has taken place approximately 30 s before the well- developed equiaxed grains started to form. Therefore, these particles developed to equiaxed dendrites floating around in the liquid. A physical model for formation of equiaxed grains based on the observation has been proposed. The experimental results on the change in multiplication rate with time could be reasonably explained by this physical model.
ISSN:0915-1559
1347-5460
DOI:10.2355/isijinternational.43.1415