The enthalpy of solidification of five Al-rich ternary alloys was measured in a DSC heat flux calorimeter and compared with thermodynamic enthalpy calculations. The fundamental intricacies involved in calculating a "latent" heat for alloys with a freezing range are pointed out. Various phase diagrams of the Al−Ce−Si system were calculated based on a thermodynamic description as detailed below. They were used for an interpretation of the grain refinement potential of Ce in Al-Si alloys.
The ternary Al−Ce−Si phase equilibria were investigated using X-ray diffraction methods, metallography, scanning electron microscopy with energy- and wave-length-dispersive X-ray microanalysis and differential thermal analysis. The main focus was on the Al-rich corner and the phases in equilibrium with (Al). Key experiments were selected by preliminary thermodynamic calculations. A consistent thermodynamic description was developed using the Calphad method incorporating all experimental data. A thermodynamic assessment for the binary Ce-Si system was also performed. Two ternary phases, Ce(Si1-xAlx)2 (τ1) and AlCeSi2 (τ2) were confirmed. The phase Al2CeSi2 (τ4) was sporadically observed, but is apparently metastable. The earlier reported phase Al4Ce3Si6 could not be confirmed.