PREDICTION OF THE HIGH-GRADIENT ABSOLUTE STABILITY OF THE UNIDIRECTIONAL SOLIDIFICATION INTERFACE

The stability of a liquild-solid interface during the unidirectional s olidification of a dilute binary alloy is further analyzed based on th e MS interface stability theory by incorporating mathematical deductio n with numerical calculation. A new phenomenon, the high gradient abso lute stability (HGAS) which is independent of solidification velocity, is predicted. The critical condition for this kind of absolute stabil ity, namely the critical temperature gradient formula expressed in ter ms of system characteristics, is theoretically given. The critical tem perature gradient values for HGAS of several typical alloys calculated with the obtained formula are all beyond the order of 10(3)K/mm, whic h can only be attained in the metal surface rapid re-solidification by means of high energy beans.