Directional solidification of Ti6Al4V ingots with an electromagnetic cold crucible by adjusting the meniscus

Abstract

Two different Ti6Al4V ingots were directionally solidified with an electromagnetic cold crucible using same parameters except the meniscus. Macrostructures of the two ingots were similar at the beginning of crystal growth, but became opposite at the end of crystal growth - the solid/liquid (S/L) interface is convex for one and concave for the other. Analysis of heat transfer during this cold crucible directional solidification showed that the meniscus influenced the macrostructure by changing the type of lateral heat transfer and the distance of heat conduction in axial direction. By increasing the mass of the meniscus, the lateral heat transfer changes from radiation to the combined action of radiation and heat conduction, and finally to heat conduction only. The distance of heat conduction increases at the same time. In order to achieve directional solidification, the meniscus must be kept at an optimal position in the electromagnetic field and must have appropriate size. © 2012 ISIJ.