A. Saccone

Alloying behaviour of indium with rare earths

Abstract The data in the literature relevant to the phase diagrams of the RIn systems (R ≡ rare earth) are analysed, and recent measurements of the melting temperatures of a few selected alloys of the RIn systems are reported. Experimental data from various laboratories are also compared and discussed in connection with the general methodologies applied to the study of state diagrams. On the basis of the various data available, a number of values for the characteristic constants of the existing phases are given; these values are considered to be highly reliable and include the melting temperature, the peritectic temperature, lattice parameters etc. The trends of these values, which are expressed as reduced parameters, are discussed. The regularities of these trends and their applicability to the forecasting of phase diagrams are demonstrated. The PmIn phase diagram is calculated as a specific example.

The samarium-magnesium system: A phase diagram

Abstract The samarium-magnesium system has been investigated by means of differential thermal analysis, X-ray diffraction, metallography and microprobe analysis. Five intermetallic compounds have been found to exist: SmMg (m.p. 800°C), SmMg2 (m.p. 750°C), SmMg3 (decomposes at 700°C), SmMg5 (decomposes at 565 °C) and Sm5Mg41 (peritectic decomposition). Eutectic points occur at 45.0 at.% Mg (785°C), 64.5 at.% Mg (735°C) and 92.0 at.% Mg (530°C). A eutectoidal reaction is observed at 580 °C and 20.0 at.% Mg. The crystal structures of the intermediate phases have been confirmed or determined and the lattice parameters measured.

The R3In5 and R3Tl5 phases of the rare earths

Abstract The binary intermetallic compounds R 3 X 5 (R ≡ La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Y) of the rare earths with indium and thallium were studied by the X-ray powder method. These phases resulted in a structure related to the oC32 Pu 3 Pd 5 type. The volumetric data of these alloys were compared with those for other R-In and R-Tl phases and were related to other properties (such as the melting temperatures, ΔH (formation) etc.) using different models, particularly those proposed by Wang and by Gschneidner.

Heats of formation of lanthanum-antimony alloys

Abstract Heats of formation in the LaSb system have been measured using a small furnace isoperibol calorimeter. The compositions and states of the alloys prepared in the calorimeter were checked by metallographic and X-ray analyses. The following values of ΔHform (kcal (g atom)−1 ± 0.5) were obtained for the various compounds, for reaction in the solid state at 300 K: La2Sb, −23.4; La5Sb3, −25.5; La4Sb3, −28.4; LaSb, −31.2; LaSb2, −22.0. The experimental data are discussed briefly and found to be in good agreement with those computed according to Miedemas model and, for the La-rich alloys, also with those calculated according to Kubaschewskis suggestion based on the effective coordination number.

Alloying behaviour of manganese with basic metals: PrMn system

Abstract The general properties of rare earth-manganese alloys are described and reviewed. The Pr-Mn system was studied using differential thermal analysis, X-ray examination, metallography and microprobe analysis. Both the stable phase diagram and information on the metastable equilibria were obtained. Evidence of the peritectic formation (790 °C) of Pr6Mn23 (Th6Mn23-type structure) and the decomposition (about 650 °C) of the same phase appears in the stable diagram. A eutectic (660 °C, 25 at.% Mn) was also observed. The peritectic formation (740 °C) of PrMn2 (hexagonal Laves phase) took place under metastable conditions. The various methods of preparing these alloys are discussed and their strong reactivity with alumina is studied. Finally it is shown that the Pr-Mn diagram fits well in the sequence of the known diagrams of manganese with the rare earths and the basic metals. The relation between the ratio of the atomic dimensions, the valence electron number and the mutual reactivity is emphasized.

Rare earth alloying systematics: Thallium alloys, a review

Abstract The data in the literature relevant to the intermediate phases and to the state diagrams of the R-Tl systems (R ≡ rare earth) are analysed and discussed in connection with the methodologies applied to the study of the alloy constitution. On the basis of the various data available, a number of values for the characteristic constants of the existing phases have been assessed: these values include the melting, peritectic and eutectic temperatures, the enthalpies of formation, the lattice parameters, etc. The trends of these values, in some cases expressed as reduced parameters, are discussed. The regularities of these trends and their applicability to the optimization and prediction of phase equilibria data are shown. The promethium-thallium and the “misch metal”-thallium phase diagrams are calculated and serve as specific examples. It can be seen, moreover, that all these regularities can be included in a systematic description of the general rare earth alloying behaviour: particular attention is given to the analogies between indium and thallium alloys.

Heat content of magnesium-lead alloys

Abstract The heat contents of selected MgPb alloys have been measured in the temperature range 100–760 °C using a new drop calorimeter. The results are compared with the values calculated by means of an optimization program. Heats of melting of Mg2Pb and of the eutectics have been obtained. A cursory redetermination of the formation enthalpy of Mg2Pb has also been carried out.

Phase equilibria in the praseodymium-indium system

Abstract The Pr-In system has been studied in the composition range 30–100 at.% In by differential thermal analysis, metallography and X-ray examination. The Pr-rich alloys have been reinvestigated and confirmed. The following intermediate phases were observed: Pr3In (decomposes at 930 ± 10 °C), Pr2In (decomposes at 1020 ± 10 °C), Pr1+xIn (m.p. 1170 ± 15 °C), ≈Pr3In5 (m.p. 1190 ± 15 °C) and PrIn3 (m.p. 1210 ± 15 °C). As well as the Pr-rich eutectic, three other eutectics occur: Pr1+x-In≈Pr3In5 (1110 + 10 °C, 54.0 ± 0.5 at.% In), ≈Pr3In5-PrIn3 (1130 ± 10 °C, 65.0 ± 0.5 at.% In) and PrIn3-In (155 °C, ⩾99.5 at.% In). The crystal structures of Pr3In (ordered-disordered cP4, AuCu3 type), Pr2In (hP6, Ni2In type) and PrIn3 (cP4, AuCu3 type) have been confirmed. An oC32, Pu3Pd5-type structure has been proposed for the approximate Pr3In5 phase. The characteristics of the phase diagram are compared with those of the La-In and Nd-Tl systems. The molar volumes of the Pr-In alloys are discussed and compared with those of a number of binary rare earth alloys.

Heats of formation of yttrium-antimony alloys

Abstract The heats of formation of the Y-Sb system have been,measured using a differential direct isoperibol calorimeter. The following values (kcal (g atom) −1 ) were obtained for the various compounds (reaction in the solid state at 300 K): Y 3 Sb, ΔH from = −15.3 ± 0.5; Y 5 Sb 3 , ΔH from . = −23.0 ± 0.5; YSb, ΔH from . = −25.0 ± 0.5. The composition and state of the samples were checked by chemical, metallographic and X-ray analyses. The data have been compared with those obtained for the Y-Bi and Nd-Sb systems and discussed briefly.

Phase equilibria in the neodymium-thallium system

Abstract The Nd-Tl system has been studied by differential thermal analysis, chemical analysis, metallography and X-ray examination. The following intermediate phases were observed: Nd3Tl (decomposes at 795 ± 10 °C), Nd2Tl (decomposes at 1045 ± 10 °C), Nd5Tl3 (decomposes at 1095 ± 10 °C), NdTl (m.p. 1280 ± 15 °C), Nd3Tl5 (decomposes at 1100 ± 10 °C) and NdTl3 (m.p. 1065 ± 10 °C). Three eutectics occur: Nd-Nd3Tl (785 ± 10 °C), Nd3Tl5-NdTl3 (1045 ± 10 °C) and NdTl3-Tl (300 ± 5 °C); there is a eutectoidal reaction at 685 ± 10 °C (the decomposition temperature of β-Nd). The thermal and crystallographic data obtained and the results of the thermodynamic analysis of the Nd-rich end are discussed and compared with those of similar previously known systems.