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Experimental test of morphological stability theory for a planar interface during rapid solidification
 

Summary: Experimental test of morphological stability theory for a planar interface
during rapid solidification
David E. Hoglund
Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
Michael O. Thompson
Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853
Michael J. Aziz*
Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
Received 2 October 1997
We report a parameter-free test of the theory predicting the critical solute concentration that destabilizes a
planar solid-liquid interface in the high-velocity regime where nonequilibrium interface kinetics are important.
Rapid solidification following pulsed laser melting was used to make metastable solid solutions of silicon-tin.
Rutherford backscattering spectrometry and transmission electron microscopy were used to measure the break-
down concentration. Samples remained microsegregation free with near perfect crystallinity at tin concentra-
tions up to 10 times the maximum equilibrium solubility and 100 times that predicted by linear stability theory
with local interfacial equilibrium. These measurements, covering velocities from 1 to 10 m/s, agree with the
predictions of linear stability theory when the latter incorporates a velocity-dependent partition coefficient and
a thermodynamically consistent kinetic liquidus, and contains no adjustable parameters. We also report a
systematic increase of the breakdown concentration with increasing deviation from steady-state conditions,
which is not addressed by current stability theories, parametrized by the concentration gradient just prior to

  

Source: Aziz, Michael J.- School of Engineering and Applied Sciences, Harvard University

 

Collections: Physics; Materials Science