ZIRCONIUM TETRAFLUORIDE AS A HARDENER FOR ALUMINUM AND ALUMINUM-BASED ALLOYS

Procesi littâ, 2024, Vol 2 (156), 3-10

Abstract

The paper substantiates that the use of zirconium compounds, namely zirconium dioxide and zirconium tetrafluoride, for the introduction of zirconium into aluminum is relevant, as it allows saturating aluminum-based alloys with zirconium from its intermediate products, namely ZrF₄ or ZrO₂. The article points out the disadvantages of saturating aluminum with zirconium from the ligature. The use of ZrF₄ or ZrO₂ as zirconium donors eliminates the need to obtain technically pure zirconium and ligatures from it. The results of thermodynamic calculations of the reduction of zirconium from zirconium tetrafluoride by aluminum are presented. It is established that the reduction of zirconium to Al₃Zr is thermodynamically more likely. A flux composition containing zirconium tetrafluoride as a zirconium donor was developed for saturation of aluminum and alloys based on it with zirconium.
The composition of the flux was selected based on the analysis of the ZrF₄ - LiF state diagram, where the ratio of components was to ensure the lowest possible melting point of the mixture to increase its reactivity. The mechanism of zirconium reduction from tetrafluoride was established, according to which the presence of ternary compounds, in particular Li₂ZrF₆ or Li₃ZrF₇, which interact with aluminum, is mandatory in the flux, resulting in the formation of particles of the intermetallic compound Al₃Zr. It was found that the zirconium content in the fluxes decreased from 96 % to 34 % 15 minutes after application to the metal surface. The  recovered zirconium was transferred to the aluminum solution. The amount of zirconium tetrafluoride that should be introduced into aluminum or alloys based on it to ensure its typical content in the alloys, which, according to DSTU, is 0.2 % for AMg6l, AMg6lch, AMg10, and AMg10ch grades, was calculated. The change in the macrostructure of A7 aluminum after the introduction of zirconium from its tetrafluoride in the flux was studied. The saturation of A7 aluminum with zirconium from the flux grinds the zirconium solution in aluminum and forms a non-dendrite structure.