Thermochemistry of alloys of transition metals: Part III. Copper-Silver, -Titanium, Zirconium, and -Hafnium at 1373 K

Abstract

The enthalpies of mixing of liquid copper with liquid silver and with solid titanium, zirconium, and hafnium have been measured by high temperature reaction calorimetry at 1371 to 1373 K. A least squares treatment of the data for copper-silver alloys yields the following expression for the molar enthalpy of mixing: ΔH_mix = ϰ_Agϰ_Cu(17.66 − 5.46 ϰ_Ag) kJ mol⁻¹. The enthalpies of solution of solid titanium, zirconium, and hafnium in dilute solutions in liquid copper are all exothermic; the following values were found: -2.0 kJ mol⁻¹ for Ti, -52.5 kJ mol⁻¹ for Zr, and -46.3 kJ mol⁻¹ for Hf. These values are all significantly less exothermic than predicted by the semiempirical theory of Miedema. The enthalpies of formation of congruent melting intermetallic phases in the systems Cu-Ti, Cu-Zr, and Cu-Hf were measured by drop calorimetry or by solution calorimetry in liquid copper. The enthalpies of formation of the solid alloys have been compared with corresponding data for the liquid alloys.