Experimental investigations and thermodynamic calculation in the Al-Mg-Sc system

The isothermal section at 350 degrees C of the Al-Mg-Sc has been studied by means of optical and electron microscopy, electron probe microanalysis and X-ray diffraction. A computed version of the Al-Mg-Sc system has been produced by extrapolation from the binary systems assuming that no ternary interaction parameters are needed with the exception of those used to model the ternary solubility of the binary solid phases. A good agreement was obtained between the computed and experimental isothermal sections at 350 degrees C. A few data points obtained by thermal analysis are well fitted in the corresponding computed vertical sections. It is noteworthy, that in the computed phase diagram, a liquid miscibility appear. Even if it was not possible to experimentally confirm this point, it is strongly supported by general thermodynamic rules and the features of the three involved binary systems.