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Crystal nucleation and glass formation in metallic alloy meltsHomogeneous nucleation, containerless solidification, and bulk formation of metallic glasses are discussed. Homogeneous nucleation is not a limiting factor for metallic glass formation at slow cooling rates if the reduced glass transition temperature is high enough. Such glasses can be made in bulk if heterogeneous nucleants are removed. Containerless processing eleminates potential sources of nucleants, but as drop tube experiments on the Pd-Si alloys show, the free surface may still be a very effective heterogeneous nucleant. Combination of etching and heating in vacuum or fluxing can be effective for cleaning fairly large ingots of nucleants. Reduced gravity processing has a potentially useful role in the fluxing technique, for example to keep large metallic ingots surrounded by a low density, low fluidity flux if this proved difficult under ground conditions. For systems where heterogeneous nucleants in the bulk of the ingot need gravity to segregate to the flux-metal interface, reduced gravity processing may not be appropriate for bulk glass formation.
Document ID
19860000766
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Spaepen, F.
(Harvard Univ. Cambridge, MA, United States)
Date Acquired
August 12, 2013
Publication Date
December 1, 1984
Publication Information
Publication: ESA Fifth European Symp. on Mater. Sci. under Microgravity. Results of Spacelab 1
Subject Category
Astronautics (General)
Accession Number
86N10233
Funding Number(s)
CONTRACT_GRANT: NAS8-36516
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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