Prediction of the high gradient absolute stability of the unidirectional solidification interface

The stability of a liquild-solid interface during the unidirectional solidification of a dilute binary alloy is further analyzed based on the M-S interface stability theory by incorporating mathematical deduction with numerical calculation. A new phenomenon, the high gradient absolute stability (HGAS) which is independent of solidification velocity, is predicted. The critical condition for this kind of absolute stability, namely the critical temperature gradient formula expressed in terms of system characteristics, is theoretically given. The critical temperature gradient values for HGAS of several typical alloys calculated with the obtained formula are all beyond the order of 10³K/mm, which can only be attained in the metal surface rapid re-solidification by means of high energy beams.