Thermochemistry of alloys of transition metals: Part III. Copper-silver, -titanium, -zirconium,and -hafnium at 1373 K |
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Authors: | O J Kleppa Shunroku Watanabe |
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Affiliation: | (1) The James Franck Institute, The University of Chicago, 60637 Chicago, IL;(2) The James Franck Institute, on leave of absence from his permanent position at Research Institute of Mineral Dressing and Metallurgy, Tohoku University, Sendai, Japan |
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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: δHmix = xAgxCu(17.66-5.46 xAg) 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. |
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