Results from the international Space Station: Coarsening in solid-liquid mixtures

In any two-phase mixture that contains particles of different sizes, the large particles tend to grow while the small particles shrink in a process called coarsening. Coarsening occurs on Earth during the processing of any metal alloy and thus the coarsening process affects products from dental fillings to turbine blades. Solid-liquid mixtures are ideal systems to study this coarsening process. However, gravity can induce particle sedimentation and thus hamper the studies of coarsening in these mixtures on Earth. Using the micro- gravity environment of the Space Station it is possible to study the coarsening process in solid-liquid mixtures with reduced interference from the sedimentation that occurs on Earth. Specifically we have studied the coarsening process in systems consisting of particles of tin suspended in a liquid tin-lead alloy. A series of experiments were performed in the Microgravity Glove Box on the International Space Station in November and December 2007, with sample return in February 2008. The microstructures show that the experiments were successful. We have begun to collect data from the samples.