DIRECTIONAL SOLIDIFICATION IN AN AEROGEL FURNACE WITH HIGH-RESOLUTIONOPTICAL-TEMPERATURE MEASUREMENTS

A new facility for directional solidification of metals is presented. It is based on the principle of the power-down method, but offers much better control of the solidification process than the classical metho d due to direct optical investigation of the solidification process. T he design allows to choose independent of each other the values for th e velocity of the solid-liquid interface during solidification, the ac celeration and the temperature gradient ahead of the s/l-interface. Th is is possible due to the use of aerogels - a transparent material wit h extremely low thermal conductivity. Therefore the temperature field at the surface of a solidifying sample can be monitored optically with a spatial resolution of 20 mu m and frequency of around 3 Hz. From th e measured temperature profiles the position of the s/l-interface and the temperature gradient ahead of it is obtained. Experimental results on the solidification of some aluminium alloys are presented for illu stration purposes. (C) 1998 Elsevier Science B.V. All rights reserved.