Undercooling and Solidification.

Abstract

Undercooling investigations on liquids are of fundamental interest in studying solidification phenomena and their consequences on microstructure development. Experimental techniques to achieve a deep undercooling at slow cooling rates are reviewed. The basic ideas of nucleation theory are presented. Theoretical concepts are discussed within the frame of the present state of the art of experimental investigations with special emphasis on homogeneous versus heterogeneous nucleation. A review is given on the experimental work on rapid solidification in undercooled liquids. The concomitant theoretical progress in this field is presented with emphasis on the steady state aspects of dendrite growth. The consequences of unconstrained solidification are evaluated with respect to the formation of metastable microstructures. The central position of undercooling experiments between various rapid solidification techniques is emphasized.