Measurement of thermodynamic properties of liquid Al-Mg alloys

The activities of Mg element in liquid Al-Mg alloys were determined by electromotive force method in a cell made of BN crucible. The activities of Mg and Al as well as other thermodynamic properties were calculated from the measured EMF data. The results indicate that the Mg-concentration in the alloys at 1073 K shows a negative deviation from Rault's Law in the whole range of concentration. When X-Mg is less than or equal to 0.55, the deviation is small; when X-Mg is >0.7, the deviation becomes large. When X-Mg is <0.126, the Mg concentration curve follows Henry's Law, the Henry's constant is 0.86. The behavior of Al is characterized by ideal solution in the range of 0 less than or equal to X-Mg<0.8, which shows a positive deviation from Rault's Law in the range of 0.58<X-Mg<0.8 and a negative deviation when X-Mg is >0.8.