Interaction of a dendritic solidification front with ceramic particles

The interaction of inert particles with an advancing solid/liquid interface has been investigated under low gravity conditions in the TEMPUS facility during parabolic flight. TEMPUS is similar to terrestrial levitation facilities, but has the advantage that the heating and the positioning coils are decoupled. This reduces the induced convection in the melt considerably compared to terrestrial levitation processing. The velocity of the solidification front can be varied by undercooling of the melt. Metallic samples with ceramic particles, which have been molten, undercooled and solidified in TEMPUS, have a clearly different microstructure than comparable terrestrial samples. While in terrestrial samples most particles are found in clusters, we find in TEMPUS processed samples many isolated particles, engulfed by the dendrites or entrapped in the interdendritic space. The results are in contradiction to standard theories describing pushing and engulfment behavior of particles with a planar solidification front. The paper summarizes results achieved in the respective part of ESA-MAP project “METCOMP”, which is dedicated to the interaction of ceramic particles with a dendritic solid/liquid-(s/l)-interface.