A WITHDRAWAL METHOD OF DIRECTIONAL SOLIDIFICATION OF A GASTING OF METAL OR ALLOY FOR PRODUCING A DIRECTIONALLY, SOLIDIFIED ARTICLE AND A DIRECTIONALLY SOLIDIFIED ARTICLE THUS PRODUCED

摘要

An improved method of directional solidification is provided by varying the rate of withdrawal of a casting from the hot zone of a solidification furnace according to the sense of change of the perimeter to area ratio of the casting. The rates are varied to achieve desired microstructure and resultant properties in the casting. Also, the rate of withdrawal is varied according to controlled and predetermined relationships to cause the solidification interface to move through a transition section connecting sections of differing perimeter to area ratios in a manner which produces a desired microstructure in a first, transition, and second sections.