Cell tip undercooling in directional solidification

Undercooling Delta(t) of cell tips in directional solidification of impure succinonitrile is measured with respect to pulling velocity V, thermal grad ient and cell spacing. Denoting V-c as the critical velocity of planar fron t destabilization and nu as the reduced velocity V/V (c), the relation nu D elta(t) = 1 is evidenced in the cell to near dendritic regime 1 less than o r equal to nu less than or equal to 17 with a high accuracy. Some of its co nsequences are drawn. (C) 1999 Published by Elsevier Science B.V. All right s reserved.