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Liquidus Temperatures and Solidification Behavior in the Copper-Niobium SystemThe copper-niobium phase diagram has been under active debate; thus, a corroboratory experimental study is needed. In this investigation, the melts of Cu-Nb alloys at compositions ranging from 5 lo 86 wt% Nb were processed in different environments and solidified at relatively low rates of 50-75 C/s to determine liquidus temperatures and to study solidification behavior. For all samples processed under very clean conditions, only Nb dendrites in a Cu matrix were observed; while in the presents of oxygen impurities, the alloys containing 5-35 wt% Nb exhibited microstructure of Nb-rich spheroids and Nb dendrites in the Cu matrix. The results obtained from clean conditions are in fair agreement with the Cu-Nb phase diagram having an S-shaped, near-horizontal appearances of the liquidus. The formation of Nb-rich droplets at slow cooling rates is discussed in terms of a stable liquid miscibility gap induced by oxygen.
Document ID
19990021537
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Li, D.
(National Academy of Sciences - National Research Council Huntsville, AL United States)
Robinson, M. B.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Rathz, T. J.
(Alabama Univ. Huntsville, AL United States)
Williams, G.
(Alabama Univ. Huntsville, AL United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1998
Publication Information
Publication: Acta Materialia
Publisher: Elsevier Sciences Ltd.
Volume: 46
Issue: 11
ISSN: 1359-6454
Subject Category
Metallic Materials
Distribution Limits
Public
Copyright
Other

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