The System Al ₂ O ₃ ‐Cr ₂ O ₃ ‐Sio ₂

Abstract

Liquidus phase equilibrium data are presented for the system Al 2 O 3 ‐Cr 2 O 3 ‐SiO 2 . The liquidus diagram is dominated by a large, high‐temperature, two‐liquid region overlying the primary phase field of corundum solid solution. Other important features are a narrow field for mullite solid solution, a very small cristobalite field, and a ternary eutectic at 1580°C. The eutectic liquid (6Al 2 O 3 ‐ICr 2 O 3 ‐93SiO 2 ) coexists with a mullite solid solution (61Al 2 O 3 ‐10Cr 2 O 3 ‐29SiO 2 ), a corundum solid solution (19Al 2 O 3 ‐81Cr 2 O 3 ), and cristobalite (SO 2 ). Diagrams are presented to show courses of fractional crystallization, courses of equilibrium crystallization, and phase relations on isothermal planes at 1800°, 1700°, and 1575°C. Tie lines were sketched to indicate the composition of coexisting mullite and corundum solid solution phases.