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Growth Competition During Double Recalescence in Fe-Cr-Ni Alloys

Published online by Cambridge University Press:  10 February 2011

D. M. Matson
D. M. Matson*
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, matson@mit.edu
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Abstract

The rapid solidification of a Fe- 12wt%Cr- 16wt%Ni alloy was investigated under containerless processing conditions using both ground-based electromagnetic levitation equipment and aboard the shuttle Columbia using the TEMPUS facility. A high-speed digital video technique was used to image growth of the metastable ferritic phase and the stable austenitic phase into the undercooled melt. Above a critical undercooling, the metastable phase nucleates first. After a delay, a second thermal rise is observed during transformation to the stable phase. Double recalescence events were observed at temperatures consistent with the To, temperature of the bcc phase thus defining a value of the critical undercooling for metastable nucleation which is significantly lower than previously predicted. For a given liquid temperature the velocity of the stable fcc phase is greater than that of the metastable bcc phase. The velocity for growth of the stable phase into the semi-solid which forms during primary metastable recalescence was also measured and found to be independent of the initial undercooling. A model based on competitive growth of the two phases successfully predicts the limit where double recalescence events may be detected.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 551: Symposium JJ – Materials in Space-Science, Technology & Exploration , 1998 , 227
Copyright
Copyright © Materials Research Society 1999

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