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

Abstract

Copper-Nickel (solid) / Mass Spectrometry / Phase Diagram / ThermodynamicsSolid 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 uj 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 H E 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.

Experimental investigation and thermodynamic calculations of the Cu–In–Ni phase diagram

“…Several studies on the thermodynamic activities of liquid alloys [49][50][51][52] and enthalpies of mixing of liquid Cu-Ni alloys [53][54][55] can be found in literature. Evaluation of thermodynamic data and phase equilibria by Jansson [40] and an Mey [37] has shown that the values obtained by Tomiska and Neckel [41] are in very close agreement with the total set of thermodynamic data for this system. Thermodynamic activities for solid Cu-Ni alloys were reported by Moser et al [56], Notin et al [47], Katayama et al [57], Kontopoulos [58] and Vrestal and Stransky [59].…”

“…Solidus and liquidus temperatures of this system were experimentally determined by Feest and Doherty [33], Schürmann and Schulz [34] and Predel and Mohs [35]. Moreover, some earlier modeling of the solid-liquid equilibria has been carried out by different authors [36][37][38][39][40][41][42]. On the basis of thermodynamic calculations, Meijering [43] and Elford et al [44] have proposed the existence of a miscibility gap in the solid state at low temperatures.…”

Atom Probe Study of the Miscibility Gap in CuNi Thin Films and Microstructure Development

“…The determination of phase boundaries is not an easy task since the diffusivity is very slow at the considered temperatures and phase equilibrium can only be reached with extremely long annealing times (Johnson et al, 1986). Nevertheless, some attempts were made to clarify this issue by indirect experimental measurements and by computational methods which all support the phase separation tendency and the existence of a miscibility gap (Vrijen & Radelaar, 1978; Tomiska & Neckel, 1984; Srikanth & Jacob, 1989; Asta & Foiles, 1996). The reports, however, show large discrepancies with respect to critical temperature T C and the exact position of the binodal line.…”