Institute of Solid State Chemistry of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia:

V. M. Skachkov, Engineer
S. P. Yatsenko, Head of Laboratory, e-mail: yatsenko@ihim.uran.ru

There were researched the high-temperature exchange reactions between liquid aluminum and fluoride-chloride salt systems, containing scandium, zirconium, hafnium, and yttrium compounds. Joint reduction of scandium with zirconium, scandium with hafnium, and scandium with zirconium and hafnium can be carried out with high direct metallurgical yield to the alloy in the absence of magnesium. Only a part of yttrium (<40%) is reduced under similar conditions. Along with metal fluorides and chlorides, the technological charge should also contain aluminum fluoride and potassium hydrofluoride. These salts are favourable to the total extraction of rare metals to base metal and are conductive to the coalescence of metal drops into common ingot. Usage of scandium fluoride in the process of exchange reaction leads to higher direct yield from salt into alloy (up to 96%), in comparison with usage of scandium oxide in initial charge (<80%). Increasing of melting temperature up to 900 oС increases the direct yield of zirconium or hafnium to the alloy, but decreases the scandium yield significantly. The carried out researches have shown that obtaining of required ratios of alloying components can be easily regulated by initial concentrations of their salts in charge. There was researched the crystallization of melt with cooling rates of up to 104 K/s. There were carried out the electron-microscopic investigations of alloys with estimation of local region compositions. Sizes of inclusions are increased by up to 100 μm due to the slow cooling, using the centrifugation for separating of large intermetallic compounds. There is shown the type of intermetallic compounds, formed during the alloy quenching. Scandium forms the cubic intermetallic compounds, while introduction of cheaper zirconium and hafnium modifiers complicates the structure with formation of dendritic forms. There is shown that the alloy microhardness is increased along with the growth of cooling rate.

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