Direct observation of the columnar to equiaxed zone transition in an undercooled melt

Abstract Utilizing a succinonitrile-water mixture it was shown that a zone of equiaxed grains developed from dendrites which initiated and then detached near the point of nucleation. These fragments proceeded to sink at a rate faster than growth of the columnar dendrites, increasing in size along the way. These observations suggest a means to account for the transition observed in the Pb — 75 wt pct Sn alloys.