Experimental Study on Phase Equilibria of CaO–Al ₂ O ₃ –La ₂ O ₃ System at 1873 and 1773 K

ABSTRACT The CaO–Al 2 O 3 –La 2 O 3 slag system is a fundamental system for potential metallurgical slags applicable to rare‐earth steel (RE‐steel). Herein, we utilized high‐temperature equilibrium experiments and quenching techniques, followed by characterization via scanning electron microscopy, electron probe microanalysis, and x‐ray diffraction, to determine the morphology, composition, and type of equilibrium phases in the CaO–Al 2 O 3 –La 2 O 3 system. Based on the experimental results, isothermal sections of the system at 1873 K (consisting of nine three‐phase fields, five two‐phase fields, and one liquid‐phase field) and 1773 K (containing 11 three‐phase fields, six two‐phase fields, and one liquid‐phase field) were constructed. Thereafter, the effect of slag composition on the dissolution behavior of potential inclusions in RE‐steel, particularly A, A 11 L, AL, C 2 AL, and C 2 A 3 L, into the slag was analyzed from a thermodynamic perspective. The study on the phase diagram of the CaO–Al 2 O 3 –La 2 O 3 system can not only guide the smelting of RE‐steel but also offer a reference for the materials design and synthesis methods of La‐containing ceramic from a thermodynamic perspective.