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Surface effects on phase distributions of a fast-quenched miscibility gap type system - Succinonitrile-waterIf a binary homogeneous melt is cooled into an immiscible region, the newly formed second phase will generally have a density different from the parent phase, and will separate readily by sedimentation. Observation of solidification processes in microgravity indicates that outside of sedimentation, at least two other important effets can separate the phases: (1) preferential wetting, and (2) thermal migration of second-phase droplets due to interfacial tension gradients. The latter effect would drive the minority phase along the thermal gradient toward the hottest part (assuming the interfacial tension decreases with increasing temperature), which is usually away from the crucible wall. On the other hand, if the minority phase preferentially wets the crucible, a minority phase layer which thickens as initial solution compositions approach critical, will form adjacent to the solid surface and remain in the coldest region of the ingot. This study presents compelling preliminary evidence that these two effects do exist and that they compete with one another. However, the temperature dependence of preferential wetting below T(c) for the current system of study is, as yet, undetermined. These effects are sensitive to the initial concentration of a hypermonotectic solution cooling through a miscibility gap.
Document ID
19860036829
Document Type
Reprint (Version printed in journal)
Authors
Frazier, D. O. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Facemire, B. R. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Fanning, U. S. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1986
Publication Information
Publication: Acta Metallurgica
Volume: 34
ISSN: 001-6160
Subject Category
CHEMISTRY AND MATERIALS (GENERAL)
Distribution Limits
Public
Copyright
Other