The formation of the equiaxed crystal zone in the flowing fluid

Abstract

Various compositions of ammonium-chloride solutions were cast to study the influences of superheat and fluid flow on the formation of the equiaxed crystal zone. Various parts of residual liquid in solidifing Al-4.5%Cu alloys were quenched in water for the same purpose. The fluid motion gives rise to fluctuation of temperature at the solidification front, lowers the temperature of bulk liquid, and reduces the temperature gradient. These effects promote dendrite fragmentation, and the fragments survive. The relationship between the experimental facts and the explanation currently proposed on the origin of equiaxed zone is also discussed.