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Grain Refinement Mechanism in Undercooled Cu30Ni70

Published online by Cambridge University Press:  31 January 2011

J. Z. Xiao ,
K. K. Leung  and
H. W. Kui
J. Z. Xiao
Affiliation:
Department of Physics, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
K. K. Leung
Affiliation:
Department of Physics, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
H. W. Kui
Affiliation:
Department of Physics, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
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Abstract

When undercooled molten Cu30Ni70 crystallizes at an undercooling ΔT≅ 145 K (ΔT is defined as Tl – Tk where Tl is the liquidus of Cu30Ni70 and Tk is the kinetic crystallization temperature), its grain size undergoes a rapid decrease by as much as two orders of magnitude in a narrow temperature range. This phenomenon is termed grain refinement. It was found that grain refinement is brought about by multiplication of dendrites. Composition analysis of the dendrite indicates that it has the least Ni concentration at its axis. The Ni content then increases radially from the central axis. Therefore, the dendrite is unstable against melting since the melting temperature of Cu–Ni increases with Ni content. The origin of grain refinement is attributed to the remelting of these dendrites.

Type
Articles
Information
Journal of Materials Research , Volume 12 , Issue 4 , April 1997 , pp. 873 - 876
Copyright
Copyright © Materials Research Society 1997

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