Thermochemistry of binary alloys of transition metals: The Me-Sc, Me-Y, and Me-La (Me = Ag,Au) systems
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I.
INTRODUCTION
T H E R M O C H E M I C A L data for alloys formed by the transition metals are scarce, and the available experimental information is not broad enough to provide verification of possible theoretical predictions of alloy enthalpies of formation, tl] In recent years, we have carded out high-temperature calorimetric measurements on a number of binary alloy systems. A part of this effort has been devoted to alloys of the group IB metals with transition metals. These investigations were initiated with a study of the copper-manganese system [21 and were soon extended to the alloys of copper with the group IV metals titanium, zirconium, and hafnium t3,41 and with the group III metals scandium, yttrium, lanthanum, and lutetium, tSl Later, we also studied the liquid alloys of gold with all of the 3d elements at 1373 K , [6'7] these investigations proved the versatility of high-temperature solidliquid calorimetry as developed in this laboratory. The recent development of a new high-temperature calorimeter, the performance of which was tested at 1473 K through measurement of the standard enthalpies of formation of several intermetallic compounds, Eal stimulated our interest in alloy systems which exhibit even more stable intermetallic phases than those observed in the copper-group III systems. In the present investigation, we have determined the standard enthalpies of formarion of six congruently melting intermetaUic compounds of silver with scandium, yttrium, and lanthanum and of three compounds of gold with the same metals. We have also obtained enthalpy of mixing information at 1473 K for liquid alloys in five of the six systems. A comparison between the enthalpy data for the solid and liquid alloys provides approximate enthalpies and entropies of fusion for the compounds.
K. FITZNER, Associate Professor, is on leave from his permanent position at the Institute of Metals Research, Polish Academy of Sciences, 30-059 Krakow, Poland. W.-G. JUNG, Research Associate, and O.J. KLEPPA, Emeritus Professor, are with The James Franck Institute, The University of Chicago, Chicago, IL 60637. Manuscript submitted September 14, 1990. METALLURGICAL TRANSACTIONS A
These new data allow us to explore systematic trends not only where one group III metal is replaced by another but, also, in the case of lanthanum, where one group IB metal is replaced by another.
II.
EXPERIMENTAL
A. General The experiments were carded out at 1473 --- 2 K in a new high-temperature calorimeter which was described recently, tsl This apparatus represents a modification of calorimeters described by French groups, t9,l~ which, in turn, are improved versions of the commercial Setaram design. All experiments were performed inside a special calorimeter "liner" of 20-mm ID, the lower part of which is constructed from Pt-20 pct Rh tubing of about 0.5-mm wall thickness and of 80-cm total length. One end of the liner is closed, while the other end is silver-soldered to a stainless steel tube which is fitted with a standard 29/42 female ground joint. T
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