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Critical undercoolings for the formation of metastable phase and its morphologies solidified from undercooled Fe–Co melts

Published online by Cambridge University Press:  31 January 2011

Li Mingjun ,
Song Guangsheng ,
Yang Gencang  and
Zhou Yaohe
Li Mingjun*
Affiliation:
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an, 710072, People's Republic of China
Song Guangsheng
Affiliation:
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an, 710072, People's Republic of China
Yang Gencang
Affiliation:
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an, 710072, People's Republic of China
Zhou Yaohe
Affiliation:
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an, 710072, People's Republic of China
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

The maximum undercoolings of 304, 318, 308, and 296 K were achieved, respectively, in Fe-22, 26, 30, and 34 at.% Co alloys. The metastable bcc phase nucleated from melts when undercoolings exceeded critical ones. The critical undercoolings for the formation of metastable bcc phase from Fe-22, 26, 30, and 34 at.% Co melts were 104, 156, 204, and 248 K, respectively. The morphologies of as-obtained metastable bcc phase exhibited five typical patterns: dendrite cores with primary and second arms, well-developed second arms, and radiated, lath, and platelike structures. Based on the classical nucleation theory, the solidification behavior of the melts was analyzed with regard to the metastable phase formation when the melts were undercooled greater than critical undercoolings. The formation of various morphologies was also evaluated to consider the solidification behavior of the undercooled melts.

Type
Articles
Information
Journal of Materials Research , Volume 14 , Issue 5 , May 1999 , pp. 1679 - 1682
Copyright
Copyright © Materials Research Society 1999

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