Thermodynamics of Aluminium-Barium Alloys

The activity of barium in liquid Al-Ba alloys $(X_{Ba}\leq 0.261)$ at 1373 K has been determined using the Knudsen effusion-mass loss technique. At higher concentrations $(X_{Ba}\geq 0.38)$,the activity of barium has been determined by the pseudo-isopiestic technique. Activity of aluminum has been derived by Gibbs-Duhem integration. The concen-tration-concentration structure factor of Bhatia and Thornton$^{[22]}$ at zero wave vector has been computed from the thermodynamic data. The behavior of the mean-square thermal fluctuation in composition indicates a tend-ency for association in the liquid state. The associated solution model with $Al_5Ba_4$ as the predominant complex has been used for the description of the thermodynamic behavior of liquid Al-Ba alloys. Thermodynamic data for the intermetallic compounds in the Al-Ba system and the enthalpy of mixing in liquid alloys have been derived using the phase diagram and the Gibbs' energy of mixing of liquid alloys.