The kinetics of solid nucleation in zirconium

The framework of classical nucleation theory coupled with statistical analy sis was used to evaluate nucleation data from zirconium undercooling experi ments. Bulk samples of high purity zirconium were processed in a containerl ess, high vacuum environment using electrostatic levitation at Space System s/Loral in order to obtain sets of nucleation temperature data. The relatio nships between undercooling and initial material purity have been investiga ted. The nucleation rate equation parameters, preexponential factor and wor k of cluster formation, were determined using a statistical analysis techni que. The mean undercooling values ranged from 326 to 348 K for material pur ities between 99.8 and 99.995%, respectively. The range of values for the p reexponential factors, 10(32)-10(43), and the activation energies, 64-88 kT , for the classical nucleation rate equation also scaled with the purity le vels. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. Al l lights reserved.