Microsegregation in Peltier interface demarcation

Experimental results on solute microsegregation induced by Peltier interfac e demarcation (PID) technique during directional solidification of Bi-1 wt% Sb alloys are presented. These data are compared with the results of numer ical simulation and the theory of PID is revisited. It is shown that the Pe ltier coefficient previously determined using Peltier pulsing has been unde restimated. The quantity of interface cooling absorbed by limited Bi-growth kinetics is comparable to that covered by solute depiction, and can even b e dominant for very short pulses, so that the commonly made assumption of L ocal equilibrium at the solid-liquid interface (i.e. usual hypothesis of co nstant interface temperature during pulse marking for pure systems) should be abandoned and the right dependence of interface temperature on solidific ation velocity be included in the model, Finally, two conditions to select systems capable of efficient marking by PID microsegregation are deduced an d the effects of applied current in the first instants of electric pulse cl arified. (C) 2000 Elsevier Science B.V. All rights reserved.