Bearing materials are generally heterogeneous materials, containing hard as well as soft, phases. Hypermonotectic AlPb and AlBi alloys, especially, are considered as exceptionally qualified bearing materials if they also contain additional hard phases to decrease wear. Based on the considerable differences in the density of the decomposed fluid phases at high temperatures and the high velocity of separation, such alloys cannot, to date, be manufactured under terrestrial conditions. The results of microgravity experiments for the manufacturing of suitable sample material with a fine phase dispersion of the monotectic phases were rather disappointing. The cause of the rapid phase separation and local enrichment under microgravity conditions was found to be the Marangoni convection, the effects of which, to date, have been underestimated. The results of these space experiments are now utilized in a terrestrial casting process, whereby a comparatively high Marangoni convection is superposed in the opposite direction to the sedimentation action of gravity, thereby partially compensating the effects of gravity. Thus, cast strips of AlSiPb and AlSiBi alloys could be manufactured, the lead and bismuth phases being present in a characteristic fined ispersion over the length of the cast strips. The first tribological laboratory tests give an indication of the excellent suitability of-such advanced bearing material for the future. [References: 15]
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