Abstract
A systematic experimental investigation of the efficiency of the Peltier interface demarcation (PID) technique is carried out during the directional solidification of Bi-1 wt% Sb alloys. The contributions of the Peltier, Thomson and Joule effects to the change in interface velocity are analyzed as a function of the control parameters (pulse duration, current polarity and current density). The experimental results are quantitatively compared to those predicted by a theoretical model and show a good agreement. Moreover, we study the perturbations induced by the pulses upon the solid-liquid interface morphology and intrinsic development. Then, we are able to propose the most favorable pulse conditions which can produce a clear interface demarcation by striations without significantly affecting the over-all crystal growth process. Finally, the PID technique is applied to investigate the morphological instability of the planar interface. A time sequence of interface pattern development, delineated by the pulse marking striations, shows the initial stages of the cellular morphology. In particular, the drift of the cells along the interface, which results from anisotropic interface kinetics, is observed.
Published Version
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