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Macrosegregation in undercooled Pb-Sn eutectic alloysA novel technique resulting in large undercoolings in bulk samples (23g) of lead-tin eutectic alloy is described. Samples of eutectic composition were processed with undercoolings ranging from 4 to 20 K and with cooling rates varying between 0.04 to 4 K/sec. The final macrostructure of undercooled samples depends on both the initial undercooling of the melt and the cooling rate. Gravity-driven segregation is found to increase with increasing undercooling. A eutectic Pb-Sn alloy undercooled at 20 K and cooled at 4 K/sec had a composition of about Pb-72 wt pct Sn at the top and 55 pct Sn at the bottom. Macrosegregation in these undercooled lead-tin eutectic alloys is shown to be primarily due to a sink/float mechanism caused by the difference in density of the solid and liquid phases and the undercooling and nucleation behavior of the alloy.
Document ID
19890032250
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
De Groh, H. C., III
(NASA Lewis Research Center Cleveland, OH, United States)
Laxmanan, V.
(NASA Lewis Research Center; Case Western Reserve University Cleveland, OH, United States)
Date Acquired
August 14, 2013
Publication Date
January 1, 1988
Subject Category
Metallic Materials
Meeting Information
Meeting: Solidification Processing of Eutectic Alloys
Location: Cincinnati, OH
Country: United States
Start Date: October 12, 1987
End Date: October 15, 1987
Sponsors: Metallurgical Society of AIME
Accession Number
89A19621
Distribution Limits
Public
Copyright
Other

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