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ELSEVIER Journal of CrystalGrowth 148(1995)172-182 ........ CRYSTAL

Summary: ELSEVIER Journal of CrystalGrowth 148(1995)172-182
........ CRYSTAL
Nonequilibrium partitioning during rapid solidification
of Si-As alloys
J.A. Kittl a, M.J. Aziz a, *, D.P. Brunco b, M.O. Thompson b
aDivision of Applied Sciences, Harvard University, Cambridge, Massachussets 02138, USA
bDepartment of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
Received21 April 1994;manuscriptreceivedin finalform26September 1994
The velocity dependence of the partition coefficient was measured for rapid solidification of polycrystalline Si-4.5
at% As and Si-9 at% As alloys induced by pulsed laser melting. The results constitute the first test of partitioning
models both for the high velocity regime and for non-dilute alloys. The continuous growth model (CGM) of Aziz and
Kaplan fits the data well, but with an unusually low diffusive speed of 0.46 m/s. The data show negligible
dependence of partitioning on concentration, also consistent with the CGM. The predictions of the Hillert-Sund-
man model are inconsistent with partitioning results. Using the aperiodic stepwise growth model (ASGM) of
Goldman and Aziz, an average over crystallographic orientations with parameters from independent single-crystal
experiments is shown to be reasonably consistent with these polycrystalline partitioning results. The results,
combined with others, indicate that the CGM without solute drag and its extension to lateral ledge motion, the
ASGM, are the only models that fit the data for both solute partioning and kinetic undercooling interface response


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


Collections: Physics; Materials Science