Directional solidification in an aerogel furnace with high resolution optical 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 method due to direct optical investigation of the solidification process. The design allows to choose independent of each other the values for the velocity of the solid-liquid interface during solidification, the acceleration and the temperature gradient ahead of the s/l-interface. This is possible due to the use of aerogels - a transparent material with 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 the 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 illustration purposes. (C) 1998 Elsevier Science B.V. All rights reserved.