Droplets of Ga24Mg36Zn40 were solidified in a 3 m, helium-filled drop tube.
The solidified droplets contained uniformly distributed MgZn2 dendritic pr
imary crystals, whose number was determined as a function of droplet size.
A new model for the solidification in a gas-filled drop tube was developed.
It allows introduction, stochastically in space and time, of multiple nucl
ei with interfering thermal fields. Using classical homogeneous nucleation
kinetics, the model reproduces the size dependence of the number of primary
crystals. The crystal-melt interfacial tension is estimated at 0.0008-0.00
2 J/m(2). This low value is attributed to the polytetrahedral structural si
milarity between the melt and the MgZn2 Frank-Kasper phase. The program is
available upon request. (C) 2000 American Institute of Physics. [S0021-8979
(00)10303-2].