Grain refinement and the stability of dendrites growing into undercooled pure metals and alloys
作者:
A. M. Mullis,
R. F. Cochrane,
期刊:
Journal of Applied Physics
(AIP Available online 1997)
卷期:
Volume 82,
issue 8
页码: 3783-3790
ISSN:0021-8979
年代: 1997
DOI:10.1063/1.365740
出版商: AIP
数据来源: AIP
摘要:
We present an analysis of the stability of a dendrite against a small perturbation to the tip velocity. We find that dendritic growth in pure metals and alloys will become unstable above some upper critical undercooling&Dgr;T2*.In alloys above a critical concentration, dendritic growth may also become unstable below a lower critical undercooling,&Dgr;T1*.In the example systems studied, Ni–Cu and Ag–O, the location of these unstable regions shows remarkably close agreement with the onset of spontaneous grain refinement. We obtain values of&Dgr;T2*for Ni and Ag of 195 K and 160 K, respectively, in good agreement with the observed values of 170 K and 133–153 K. ©1997 American Institute of Physics.
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