Phase Equilibrium Relationship of CaO–Al₂O₃–Ce₂O₃–MgO System at 1573 K

Abstract

The phase diagram information of CaO–Al₂O₃–Ce₂O₃-based system is of great significance for the design and development of rare earth steel metallurgical slag system. In this paper, the phase equilibria of CaO–Al₂O₃–Ce₂O₃ system and CaO–Al₂O₃–Ce₂O₃–MgO system were determined by the high temperature equilibrium experiment at 1573K; then the isothermal section for ternary system and isothermal spatial phase diagram for quaternary system were constructed, respectively. A total of 11 kinds of equilibrium phase fields were determined in the CaO–Al₂O₃–Ce₂O₃ system, including C₂A₃Ce–ACe–C₂ACe, C₂A₃Ce–C₃A–C₂ACe, C₂A₃Ce–C₃A–CA, C₂A₃Ce–ACe–CA₂, C₂A₃Ce–CA–CA₂, C₂ACe–Ce, CA₆–ACe, C₂A₃Ce–C₂ACe, C–C₃A–C₂ACe, C–Ce–C₂ACe, and Ce–ACe–C₂ACe. A total of 10 kinds of equilibrium phase fields were determined in the CaO–Al₂O₃–Ce₂O₃–MgO system, including C₂A₃Ce–CA–CA₂–MA, C₂A₃Ce–MA–CA₈M₂–ACe, C₂A₃Ce–C₂ACe–ACe–M, C₂A₃Ce–CA–MA–M, C₂A₃Ce–ACe–MA–M, C₂A₃Ce–M, C₂A₃Ce–C₃A₂M, C–C₃A–C₂ACe–M, C₂A₃Ce–C₃A–C₂ACe–M, and C₂A₃Ce–CA₂–CA₇M–ACe. On this basis, the coexistence relation of the primary phase fields was determined and expressed in the form of alkemade lines/triangles/tetrahedrons. The alkemade lines constructed a total of 11 sub-solidus triangles (for ternary system) and 21 sub-solidus tetrahedrons (for quaternary system). Finally, the qualitative discussion was conducted on the modification laws of Al₂O₃ inclusions in rare earth steel under different RE, Ca, and Mg content conditions.