Thermodynamic aspects of the constitution, grain refining, and solidification enthalpies of Al-Ce-Si alloys
The ternary Al-Ce-Si phase equilibria were investigated using X-ray diffraction (XRD) methods, metallography, scanning electron microscopy with energy-dispersive X-ray analysis (SEM/EDX) and wavelength-dispersive X-ray microanalysis, and differential thermal analysis (DTA). The focus was on the Al-r...
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Veröffentlicht in: | Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2004-11, Vol.35 (11), p.3349-3362 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | The ternary Al-Ce-Si phase equilibria were investigated using X-ray diffraction (XRD) methods, metallography, scanning electron microscopy with energy-dispersive X-ray analysis (SEM/EDX) and wavelength-dispersive X-ray microanalysis, and differential thermal analysis (DTA). The 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(Si^sub 1-x^Al^sub x^)^sub 2^ (τ^sub 1^) and AlCeSi^sub 2^ (τ^sub 2^), were confirmed. The phase Al^sub 2^CeSi^sub 2^ (τ^sub 4^) was sporadically observed, but is apparently metastable. The earlier reported phase Al^sub 4^Ce^sub 3^Si^sub 6^ could not be confirmed. In addition, the enthalpy of solidification of five Al-rich ternary alloys was measured in a differential scanning calorimetry (DSC) heat flux calorimeter. The agreement with the thermodynamic enthalpy calculations is acceptable. 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 the thermodynamic description. They were used to quantitatively identify possible contributions to the grain refinement potential of Ce in Al-Si alloys due to the phase equilibria. [PUBLICATION ABSTRACT] |
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ISSN: | 1073-5623 1543-1940 |
DOI: | 10.1007/s11661-004-0172-y |