PHASE-FORMATION AND THERMODYNAMICS OF UNSTABLE CU-CR ALLOYS

The quantitative description of highly nonequilibrium processes for th e preparation of metastable and unstable phases requires the determina tion of the thermodynamic functions of the system under investigation. However, in systems such as Cu-Cr which are immiscible in the equilib rium states, the determination of the thermodynamic functions over the entire concentration range is often difficult if not impossible becau se reliable experimental data are not available for the metastable or unstable regime. The present paper demonstrates that such data can be obtained by a combination of thin film deposition techniques and diffe rential scanning calorimetry. It is concluded that the phase formation in such thin films can be described in terms of the thermodynamics of the system, even when the heats of mixing are highly positive. The re sults indicate that models of the regular solution type still provide a reasonable description of the thermodynamic functions of such alloys .