Thermodynamic investigation of atomic order in AlMg liquid alloys

The grand partition function has been used to obtain analytic expressions for the excess free energy of mixing, the activity, the small-angle partial structure factors and the chemical short-range order parameter for weak interacting compound-forming molten alloys. It has also been applied to explain the asymmetry in the properties of mixing of AlMg molten alloys by assuming that the chemical complex Al₃Mg₂ exists in the liquid phase. It is concluded that a reasonable degree of chemical order may exist in the concentration range 0.2<or=C_Al<or=1.0, being greatest at 60 at.% of Al. In the Mg-rich end (C_Mg>or=0.8), however the melt is close to the ideal mixture. The topological order, at least at the long-wavelength limit, has been found to depend only weakly on concentration.