Development of Composite-and-Functional Gradient Material by using Supercooling

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Solidification is due to the restriction of rotational motion of liquid molecules and results in the fixation of solid structure as a regular and/or dense assembly of atoms with release of latent heat of fusion. From the viewpoint of the way that the latent-heat extraction should be, the solidification can be largely classified into three types in relating with cooling rates.In low cooling rate, the latent heat is removed out by heat transfer and solidification proceeds quasisteadily with a solid-liquid interface kept at an equilibrium temperature. In high cooling rate, as for "rapid solidification of material processing", a supercooling state easily appears and this brings massive solidification due to crystal growth initiated by nucleation. The supercooling which makes a rapid and insitu solidification possible, may result in the formation of new meta-stable phases of crystalline and of amorphous. In intermediate cooling rate, the supercooling also appears and distributes in close region from the cooling surface to some internal position being equilibrium. These imply that the solidification proceeds under two kinds of heat extraction sources ; the initially distributed supercooling and the external cooling.The emphasis in the discussion is on fundamentals of solidification of mixtures with supercooling under external heat transfer cooling : solidification process, appearance of micro-structure and microsegregation in the solid, and macro-micro conjugation of heat transfer with the solidification.