Surface properties of oxide-fluoride compounds formed during the aluminothermic synthesis of high-entropy alloys

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This work presents thermodynamic modeling and experimental study of the oxide-fluoride phase formed during the production of high-entropy refractory, lightweight alloys of the Al–Ti–Zr–V–Nb system by the method of combined aluminothermic reduction from metal oxides of titanium, zirconium, niobium and vanadium. The aim of the work was to determine the optimal conditions for obtaining such alloys and to find the characteristics of phase separation. Modeling showed that the formation of a lightweight and refractory alloy requires temperatures of at least 1600°C and an aluminum content in the range of 15 to 40 atomic percent. In this case, it is recommended to use a small excess of aluminum in the charge to ensure the transition of some aluminum to the metallic phase. Calculations of surface tension and density showed a significant difference between the metallic and oxide-fluoride phases, which contributes to the settling of the metallic melt to the bottom of the crucible and the formation of a clear separation boundary between the two phases. Interfacial tension in the range of 1000–1600 mJ/m² ensures minimal wetting of the slag by the metal and reduces the amount of non-metallic inclusions in the metal, which has a positive effect on the quality of the final product. It is noted that an increase in the number of components in the melt complicates the selection of empirical coefficients, which limits the accuracy of the calculation by the empirical method. Chemical analysis of the oxide-fluoride phase after the experiment confirmed the presence of zirconium and titanium oxides in it, which increase the surface tension and density compared to the calculated values. However, these parameters remain below the corresponding values of the metallic phase, which ensures effective phase separation and the formation of a solid metal ingot without excessive adhesion to the oxide-fluoride phase. The results obtained demonstrate the promise of the selected conditions for the production of high-quality high-entropy alloys and can be used for further evaluation calculations and optimization of technological processes.

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Sobre autores

A. Russkih

The Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences

Autor responsável pela correspondência
Email: russkih_A_S@mail.ru
Rússia, Yekaterinburg

E. Zhilina

The Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences

Email: russkih_A_S@mail.ru
Rússia, Yekaterinburg

T. Osinkina

The Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences

Email: russkih_A_S@mail.ru
Rússia, Yekaterinburg

Bibliografia

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2. Fig. 1. Dependence of the equilibrium composition on temperature for the oxide-fluoride phase, initial batch, wt.% 18.7Al – 7.9TiO2 – 26.3ZrO2 – 9.0V2O5 – 13.2Nb2O5 – 19.3CaO – 5.5CaF2.

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3. Fig. 2. Dependence of the equilibrium composition of the oxide-fluoride phase on the consumption of the reducing agent – ​​aluminum (wt.%) during its interaction in the mixture 7.9TiO2 – 26.3ZrO2 – 9.0V2O5 – 13.2Nb2O5 – 19.3CaO – 5.5CaF2 at a temperature of 1650 °C.

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4. Fig. 3. Results of calculating the surface tension and density for metal and oxide-fluoride melts: a – surface tension, b – density.

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5. Fig. 4. Surface tension (a) and density (b) of oxide-fluoride melts upon heating.

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