In this article, we summarise the most important and interesting results of solidification experiments carried out onboard of the Mir orbital station with the Ag-germanium simulation system. We used the experimental setup of the spherical specimens embedded in a glass matrix. In order to evaluate the gravitational effect, we compared the specimens solidified on earth and under micro-gravitational conditions. Under micro-gravitational conditions, the intensity of the melt convection is greatly reduced. The results confirm unambiguously that under reduced gravitational effect the stability of the supercooled melts below the liquidus temperature increases. This is reflected in the formation of a finer microstructure. This may also be accompanied by the formation of the phases of unusual growth morphology, and also of phases with compositions that differ much more from the equilibrium composition. The formation of the primary crystals of the solid solution is accompanied by the restriction of distribution of the components between these crystals and the melt, which is reflected in the deviations of the composition of the two microstructural components. Materials research in space offers unique conditions for the examination of the behaviour of Condon systems, because it is possible to obtain the conditions in which transport of the components takes place almost exclusively by atomic diffusion. This allows to eliminate the difficult-to-predict contribution of the flow field, which depends on external and internal parameters, and inhibit a conclusive evaluation of solidification experiments.
Results of crystallization experiments with Ag-Ge alloys in microgravity
Ergebnisse von Kristallisationsversuchen mit Ag-Ge-Legierungen unter Schwerelosigkeit
Metallic Materials ; 39 , 6 ; 296-303
2001
8 Seiten, 9 Bilder, 1 Tabelle, 11 Quellen
Aufsatz (Zeitschrift)
Englisch
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