St. Petersburg Mining University, Saint-Petersburg, Russia:

S. А. Savchenkov, Postgraduate Student, е-mail: savchenkov.ltc@bk.ru

The article is devoted to the study of the process of synthesis of master alloys, the magnesium-gadolinium. Based on the analysis of diagrams of the state and requirements for fluxes for melting magnesium alloys, the composition of the salt mixture was chosen. Differential thermal analysis (DTA) determined the temperature ranges of thermal effects in the melting of components of the salt mixture KCl – NaCl – CaCl₂ – MgCl₂ – CaF₂ – GdF₃ and in the reduction of compounds of gadolinium magnesium. It is established that upon contact of the molten technological salt mixture, a complex compound of gadolinium Na₅Gd₉F₃₂ is formed, which in the preparation of Mg – Gd master alloy is a precursor for the recovery of gadolinium. As a result of a series of experimental melting, the basic laws of the synthesis of magnesium-gadolinium master alloy from the selected technological salt mixture were revealed, the main factors of the metallothermic process affecting the degree of gadolinium recovery were determined. The necessary content of the alloying element in the master alloy is achieved by preliminary adjustment of the content of the initial compound of gadolinium fluoride in the technological salt mixture. The influence of technological parameters on the yield of gadolinium in the master alloy was determined on the basis of experimental melting. The maximum yield of gadolinium — 98.4%, is achieved by using a technological salt mixture of the composition KCl – NaCl – CaCl₂ – MgCl₂ – CaF₂ – GdF₃, intensive stirring of the melt at a holding time of 25–30 minutes and a temperature of at least 720 ^оC. The microstructure, chemical and phase composition of the obtained master alloys samples were investigated. It is established that the structure of the samples of the obtained magnesium-gadolinium master is dendrites of a solid solution of α-Mg, along the boundaries of which Mg_xGd_y compounds are located.

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