A combined experimental-model approach to estimate the solidification macrostructures formed during a microgravity experiment on Ti-Al based intermetallic alloys

A computational model has been developed for a furnace and associated solidification experiment scheduled for launch on the European Space Agency (ESA) MAXUS 8 sounding rocket. The purpose of the experiment is to study the Columnar to Equiaxed Transition (CET) in a family of Ti-Al-Nb intermetallic alloys. The model predicts the heat transfer conditions within the crucible as solidification of the alloy occurs. It employs a front tracking approach to predict the solidification macrostructure and, in particular, CET formation.' Because of the microgravity nature of the experiment, the model of front tracking is based on diffusion-controlled solid growth. A significant effort is required to ensure that the alloy solidifies within the limited microgravity time and that the thermal parameters are correct for a CET to occur. To this end, the model is a key tool for assisting with the development of the experiment. Confidence in the model has been built from experience gleaned from a similar ESA microgravity CET experiment performed on Al-7wt%Si. In addition, several ground-reference experiments have been performed on the Ti-Al-Nb alloy to enhance knowledge of the relevant solidification phenomena and to test the hardware before the MAXUS 8 launch. Preliminary results of this pre-launch study using the model are discussed. A formal Design of Experiments (DOE) approach is considered for supporting the experimental work. The alloy in question is significant for a European Commission research project called IMPRESS (Intermetallic Materials Processing in Relation to Earth and Space Solidification).