Thermochemistry of alloys of transition metals: Part IV. Alloys of copper with scandium, yttrium, lanthanum, and lutetiu
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I.
INTRODUCTION
R E C E N T studies of the thermodynamics of transition metal systems have drawn attention to the fact that thermochemical data for alloys formed by the early transition metals are very scarce. This is not surprising in view of the fact that these metals tend to be both fairly refractory and highly reactive; hence they are difficult to handle by high temperature thermochemical methods. This lack of data is particularly regrettable since some of these systems may offer possible checks of theoretical predictions of alloy enthalpies of formation. Recently new enthalpy of mixing data for liquid alloys of copper with manganese, 2 and with the group IV metals titanium, zirconium, and hafnium, 3'4 based on solid-liquid calorimetry at 1373 K, have been reported from this laboratory. These investigations are now extended to the alloys of copper with the group III metals scandium, yttrium, lanthanum, and lutetium. Lanthanum melts at 1193 K; it was therefore possible to study the liquid alloys of copper + lanthanum over the complete range of compositions. Since the melting points of scandium (1811 K), yttrium (1799 K), and lutetium (1925 K) all lie several hundred degrees above the operating temperature of our calorimeter, the liquid alloys of these metals with copper were studied over more limited ranges of composition. In the present investigation we have also carried out heat content measurements at 1373 K and, in one case, heat of solution measurements in liquid copper, on eight congruent melting intermetallic compounds in the copper-scandium, copper-yttrium, and copper-lanthanum systems. These measurements, in conjunction with the new data for the liquid alloys, have allowed us to derive enthalpies of formation of the intermetallic compounds. A comparison between the enthalpy data for the solid and liquid alloys also provides SHUNROKU WATANABE has a permanent position at Research Institute of Mineral Dressing and Metallurgy, Tohoku University, 1,1 Katahira 2-chome, Sendal 980, Japan. O.J. KLEPPA is Professor, Departments of Chemistry and of Geophysical Sciences, and the College, University of Chicago, James Franck Institute, 5640 South Ellis Avenue, Chicago, IL 60637. Manuscript submitted May 19, 1983. METALLURGICALTRANSACTIONS B
information on the enthalpies and entropies of fusion of the compounds. Finally, we have in the course of the present study carried out heat of solution measurements on chromium and vanadium in liquid copper. Since the solubilities of these metals in copper at 1373 K are quite low ( - 1 . 5 at. pct for Cr and - 0 . 4 at. pct for V), 5'6 the experiments were very difficult and the results must be considered as approximate. Even so, as a result of these measurements we now have calorimetric enthalpy of solution data for all the first row transition elements in liquid copper; we shall compare these values with the predictions of Miedema et al. 7 For many of these solutes in copper excess Gibbs energy data either are available from equilibrium or emf work 8'9 (Ni, Mn), or may be c
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