Thermodynamics of Solid Cu—Ni Alloys by Knudsen Cell Mass Spectrometry and Re‐Calculation of the Phase Diagram

Abstract

AbstractSolid Cu—Ni alloys have been investigated thermodynamically within the whole range of composition by Knudsen Cell Mass Spectrometry. The “Algebraic Intensity‐Ratio”‐method (A.I.R.) has been used for the determination of the thermodynamic mixing behavior. The thermodynamic activities aj show positive deviations from Raoult's law. The molar enthalpies of mixing HE and the molar excess Gibbs energies GE are positive over the whole range of composition. At 1350 K the maximum value of HE is 2420 J/mol (59.48 at‐% Ni), and the maximum value of GE is 3220 J/mol (53 at‐% Ni). The excess entropies SE are negative over the whole range of composition with a minimum value of — 0.719 J/mol · K at 36.71 at‐% Ni. The phase diagram has been re‐evaluated by using an analytical procedure which is based on the generalized Newton method for the numerical solution of equations. The calculations are based on the thermodynamic data obtained in this study, on the thermodynamic results from mass spectrometric studies on liquid Cu—Ni alloys, and on literature data for the heat capacities and the heats of melting of Cu and Ni.