THERMODYNAMIC PROPERTIES OF METASTABLE AG-CU ALLOYS

The enthalpies of formation of metastable fcc Ag-Cu solid solutions, p roduced by ball milling of elemental powders, were determined by diffe rential scanning calorimetry. Experimental thermodynamic data for thes e metastable alloys and for the equilibrium phases are compared with b oth calculation of phase diagrams (CALPHAD) and atomistic simulation p redictions. The atomistic simulations were performed using the free-en ergy minimization method (FEMM). The FEMM determination of the equilib rium Ag-Cu phase diagram and the enthalpy of formation and lattice par ameters of the metastable solid solutions are in good agreement with t he experimental measurements. CALPHAD calculations made in the same me tastable regime, however, significantly overestimate the enthalpy of f ormation. Thus, the FEMM is a viable alternative approach for the calc ulation of thermodynamic properties of equilibrium and metastable phas es, provided reliable interatomic potentials are available. The FEMM i s also capable of determining such properties as the lattice parameter which are not available from CALPHAD calculations.