Thermodynamic Description of Al-Si-Mg-Ce Quaternary System in Al-Rich Corner and Its Experimental Validation

In order to establish a self-consistent thermodynamic database for Al-Si-Mg-Ce quaternary system, all the thermodynamic descriptions of 6 boundary binaries, i.e., Al-Mg, Al-Si, Al-Ce, Mg-Si, Mg-Ce, and Si-Ce were first unified. Then, the thermodynamic descriptions for ternary Al-Mg-Ce system were re-assessed using the CALculation of PHAse Diagrams (CALPHAD) method based on all the critically reviewed experimental phase equilibria. Moreover, the consistency between thermodynamic descriptions for Al-Si-Ce ternary system and those for the unified binaries was checked and confirmed. Subsequently, the thermodynamic database for the Al-Si-Mg-Ce quaternary system was established by combining the four ternary subsystems, and the phase equilibria/thermodynamic properties of the quaternary system were predicted via direct extrapolation from the ternary systems. The reliability of the established database was finally validated in one Al-7Si-0.6Mg-0.4Ce quaternary model alloy by comprehensively comparing its experimentally measured phase transition temperatures and solidified microstructure characteristics with the Gulliver-Scheil simulation ones. Good agreement between the thermodynamic predictions and experimental results indicates the present thermodynamic database is reliable.