Theoretical Analysis and Model Study of the Formation of Channel-Type Segregation

Abstract

A mathematical model of a channel-type segregation is developed on the basis of the stability theory. By focusing on the difference of the cooling conditions, the instability phenomena inducing the segregation are theoretically analyzed by use of the model.
The analytical results are confirmed by the model experiments. In these experiments, the aqueous solutions of NH₄Cl are freezed by cooling from the top or the bottom of a mold having the adiabatic side walls or by cooling through the side walls.
Thermal insulation of the side walls are essential for preventing the channel-type segregation. When a mold is cooled through its side walls, controlled preparation of the alloy elements is required to prevent the formation of segregation.