Ternary system Al2O3-MgO-CaO: Part II, phase relationships in the subsystem Al2O3-MgAl2O4-CaAl4O7

Solid-state compatibility and melting relationships in the subsystem Al2O3- MgAl2O4-CaAl4O7 were studied by firing and quenching selected samples locat ed in the isopletal section (CaO . MgO)-Al2O3. The samples then were examin ed using X-ray diffractomtery, optical microscopy, and scanning and transmi ssion electron microscopies with wavelength- and energy-dispersive spectros copies, respectively. The temperature, composition, and character of the te rnary invariant points of the subsystem were established. The existence of two new ternary phases (Ca2Mg2Al28O46 and CaMg2Al16O27) was confirmed, and the composition, temperature, and peritectic character of their melting poi nts were determined, The isothermal sections at 1650 degrees, 1750 degrees, and 1840 degrees C of this subsystem were plotted, and the solid-solution ranges of CaAl4O7, CaAl12O19, MgAl2O4, Ca2Mg2Al28O46, and CaMg2Al16O27 were determined at various temperatures. The experimental data obtained in this investigation, those reported in Part I of this work, and those found in t he literature were used to establish the projection of the liquidus surface of the ternary system Al2O3-MgO-CaO.