Evidence of nonequilibrium processes in rapid solidification of undercooled metals

Containerless undercooling in an electromagnetic levitation device was used to observe solidification velocities as a function of undercooling temperature for pure Ni and Cu-Ni alloys. In a limited temperature range, the results can be interpreted using current theories, provided the conditions for local equilibrium at the solid-liquid interface are relaxed. Beyond a certain undercooling value, the observations differ markedly from current predictions.