Thermodynamic Assessments of the Al2O3-Al4C3-AlN and Al4C3-AlN-SiC Systems

A thermodynamic dataset for the Al2O3-Al4C3-AlN system was reassessed and that of the Al4C3-AlN-SiC system was developed in present study for the first time based on available literature data using the CALPHAD approach. In the Al2O3-Al4C3-AlN system and its subsystems the liquid was described as single phase using the partially ionic liquid model , which covers compositions from the metallic liquid to the oxide, carbide and nitride liquids. The compound energy formalism was used for modeling of the solid phases in both studied systems. Ternary phases gamma and beta of the Al4C3-AlN-SiC system were treated as stoichiometric compounds. A four sublattice model was proposed in order to describe the alpha-solid solution forming between the isostructural Al5C3N and Al4SiC4 binary phases. Using the derived datasets the isothermal sections at 1600, 2273 and 2373 K for the Al2O3-Al4C3-AlN system and at 2133 K for the Al4C3-AlN-SiC system were constructed. The calculated phase diagrams of both ternary systems were compared with the available experimental data.