Alkaline‐Earth‐Fluoride—LaF3 Systems with Implications for Electroslag Melting

Abstract

Liquidus and solidus curves in the systems CaF2‐LaF3, SrF2‐LaF3, BaF2‐LaF3, and MgF2‐LaF3 under ½ atm helium pressure were determined by thermal analysis as an aid in the selection of suitable fluxes for electroslag melting of reactive metals. The systems CaF2‐LaF3, SrF2‐LaF3, and BaF2‐LaF3 each contain (1) one eutectic, (2) no intermediate phases, and (3) two solid solutions whose lattice parameters vary linearly with composition. The liquidus curves in the systems SrF2‐LaF3 and BaF2‐LaF3 exhibit maxima. The system MgF2‐LaF3 is of the simple eutectic type with no detectable terminal solid solutions. The smallest temperature interval observed between a fluoride‐flux liquidus and the melting point of Ti occurs at the dystectic composition in the system SrF2‐LaF3. Differences in density between metal and flux are more favorable in the system BaF2‐LaF3 than in pure LaF3. These observations suggest potential advantages of using fluxes from the systems studied for electroslag melting of reactive metals.