Phase equilibria of the Al-Li binary system

The solid + liquid phase equilibria between α-Al and β-AlLi were determined using differential thermal analysis (DTA), metallography, and chemical analysis. Boron nitride (BN), which was found to be inert to these alloys, was used as the container. These measurements were carried out in order to resolve the discrepancies reported in the literature. The α-Al+β-AlLi eutectic temperature and composition were determined to be 600 °C±1 °C and 25.8±0.5 at. pct Li. Using these data and data reported in the literature concerning the phase equilibria and thermodynamic properties, thermodynamic models for all the phases were obtained by optimization. The thermodynamic values obtained for the β-AlLi phase describe not only the phase equilibria, but also yield structural defect data in agreement with measured values. The assessed enthalpies of formation, excess entropies of formation, and entropies of melting for all the intermetallic phases obtained are compared with empirical correlations when experimental data are not available. In addition to the stable diagram, a metastable diagram involving the δ′-Al₃Li is also calculated from the thermodynamic models. The calculated diagram is in good agreement with the experimental data.     

Phase equilibria in vanadium-rich alloys of the V-Ni-Al system

Vanadium-rich alloys of the V-Ni-Al system were studied by the methods of metallographic, x-ray diffraction, and electron beam microprobe analysis. The boundaries of the phases, and the vertices of the conoidal triangle αβσ, in the vanadium corne, of the 1200°C isothermal section were determined. The maximum solubility of aluminum in the σ-phase is 6 at. %. The homogeneity range of the NiAl-based β-phase is very broad; the maximum solubility of vanadium in β reaches 41.5 at. %. The maximum solubility of nickel in the vanadium solid solution is 25 at. %. Alloys containing 15–20 % Al and 20–30% Ni exhibit a tendency to dispersion haraen and, therefore, might serve as a basis for the development of a new generation of radiation-resistant materials. Institute of Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 43–47, July–August, 1997.     

Phase equilibria in Mg-Y-Gd-Sm alloys

Differential thermal, metallographic, and electron microprobe analyses are used to study the effect of samarium on the temperatures and character of the phase equilibria in Mg-rich Mg-Y-Gd alloys containing up to 5 wt % yttrium or gadolinium and up to 8 wt % samarium. The magnesium solid solution is found to be in equilibrium only with the Mg₄₁Sm₅ and Mg₂₄(Y,Gd)₅ phases, which belong to the binary Mg-Sm and ternary Mg-Y-Gd systems, respectively. Partial polythermal sections of the Mg-Y-Gd-Sm phase diagram are constructed for the Mg-rich region.     

Phase equilibria in the solidification range of alloys of the Ti-Ru-Ir system

Conclusions The processes taking place during solidification of the alloys of the Ti-Ru-Ir ternary system have been examined for the first time. The results show that the system contains three nonvariant quaternary equilibria with the liquid of the incongruent type: L + + at 2220°C, L + + at 1920°C, and L + + at 1465°C.In the region with the composition 0–50% Ti, the processes take place in the direction to the Ti-Ru side of the concentration triangle where they are also completed at the temperature of the binary eutectic L '+ equal to 1855°C. In the region with the composition 50–100% Ti the processes are completed at 1460°C at the nonvariant point corresponding to the eutectic reaction L + of the Ti-Ir binary system.Translated from Poroshkovaya Metallurgiya, No. 11(299), pp. 72–77, November, 1987.     

Phase equilibria in Al-rich Al-Sc-Cr alloys

Phase equilibria in aluminum alloys containing up to 1.2 wt % Sc and 1.0 wt % Cr are studied by optical microscopy and differential thermal and electron microprobe analyses. Two vertical sections and the projection of liquidus surface have been constructed. The four-phase nonvariant equilibrium at a temperature of 656.5 ± 1°C is found to have a transition character. The Al-based solid solution is found to be in equilibrium only with the Al₃Sc and Al₇Cr binary phases.     

Phase equilibria in prototype Nb-Pd-Hf-Al alloys

The phase equilibria in two prototype alloys with nominal compositions 60Nb-20Pd-10Hf-10Al and 40Nb-30Pd-15Hf-15Al (in at. pct) are investigated using scanning electron microscopy and X-ray diffraction. The alloys were heat treated at 1200 °C and 1500 °C for 200 hours each. The phase analysis revealed that the alloys were, for the most part, in the three-phase equilibrium between (Nb), Pd₂HfAl, and Pd₃Hf. The compositions of these three phases along with other observed phases such as PdAl and (α-Hf) provide important data for establishing the Nb-Pd-Hf-Al quaternary phase diagram. A preliminary Nb-Pd-Hf-Al phase diagram, with pertinent tie-tetrahedra, was constructed based on the available composition data. The lattice parameters of (Nb), Pd₂HfAl, Pd₃Hf, and the coefficient of thermal expansion of Pd₂HfAl were measured, and models were developed to predict the composition dependence of the mean atomic volumes/lattice parameters of (Nb) and Pd₂HfAl and the temperature dependence of the lattice parameter of the (Nb) phase. The validity of the models was confirmed by good agreement between predicted and experimental values.     

Phase equilibria in the titanium corner of hypoeutectic alloys in the Ti-Nb-Si-Al system

Physicochemical analysis methods have been applied to the phase equilibria in the Ti-Nb-Si-Al system in the region of alloys rich in titanium. It is found that the crystallization conditions for hypoeutectic alloys with constant 5 at.% aluminum content control the niobium contents up to 17.5 at.%, for which there are two groups. After the primary crystallization of the β phase in alloys in these groups, binary eutectics are formed with different intermetallic phases. The properties of the alloys are dependent on the phase compositions in the eutectic mixtures. The temperature and concentration stability of the phases have been determined. It is shown that a peritectic reaction may give rise to a second intermetallide phase in alloys approximating to equilibrium as a result of subsequent annealing, which does not affect the structure of the cast alloys.     

Phase equilibria investigations on the aluminum-rich part of the binary system Ti-Al

The binary system Ti-Al has been reinvestigated in the composition range of 50 to 76 at. pct Al by X-ray diffraction, metallography, electron probe microanalysis (EPMA), and differential thermal analysis (DTA). Heat-treated alloys (600°C to 1300°C) as well as the as-cast alloys were investigated. Seven stable intermetallic phases were observed: TiAl, Ti_1−x Al_1+x , Ti₃Al₅, TiAl₂, Ti₅Al₁₁, TiAl₃ (h), and TiAl₃ (1); two metastable phases, TiAl₂ (m) and TiAl₃ (m), were also found. For each of these phases, the homogeneity range and the crystal chemical parameters were determined. The temperatures of the solid-state phase reactions were re-established. On the basis of the experimental results, an improved version of the equilibrium phase diagram has been drawn and critically compared with earlier versions presented in the literature.     

Phase equilibria in solid Mg-Rich Mg-Sm-Tb alloys

The structure of Mg-rich Mg-Sm-Tb alloys with samarium and terbium contents up to 30 at % each is studied by metallography, electron microprobe analysis, and electrical resistivity measurements. The magnesium-based solid solution is found to be in equilibrium only with the Mg₄₁Sm₅ and Mg₂₄Tb₅ phases belonging to the Mg-Sm and Mg-Tb binary systems composing the ternary system, respectively. The individual and total samarium and terbium solubilities in a magnesium-based solid solution at 500 and 300°C are determined. The terbium and samarium solubilities in the Mg₄₁Sm₅ and Mg₂₄Tb₅ phases, respectively, are also determined. Partial isothermal sections at 500 and 300°C of the Mg-Sm-Tb phase diagram in the Mg- rich region are constructed.     

Phase equilibria in the system Zr-W-C

Summary The system Zr-W-C was investigated by the methods of X-ray diffraction and microstructural analyses. Phase equilibria at 1500°C were determined for as-cast and annealed alloys. The carbide ZrC dissolves 34 mo%WC at 500°C; at l,950°C. the solubility ofWC increases to 40 mol.'yo. As-cast alloys contain the - phase, which has a cubic NaCl-type structure (a = 4.25–4.30 A), and is distributed along the 50 at.% C line at 2–10 at.% Zr. It is shown that the solubility of WC in ZrC may be even greater at temperature approaching the melting point of the alloys.     

Phase equilibria in the system Al-Rh

Methods of differential thermal analysis, x-ray diffraction, microstructural analysis and electron probe microanalysis are used to study alloys of the Al-Rh system over the whole concentration range. It is established that the phase of equiatomic composition AlRh melts congruently at 2060°C and it has an extended range of homogeneity (45.1–54.2 at.% Rh). The solubility of aluminum in rhodium reaches 9 at.%, decreasing to 6 at.% at 850°C. Coordinates are determined for the eutectic point l ⇆ AlRh + 〈Rh〉 as 70 at.% Rh and 1715°C. The existence of intermediate phases, their crystal structure, and also the method of forming phases in the field of composition rich in aluminum given in publications are confirmed. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(449), pp. 48–56, May–June, 2006.     

Phase equilibria in the titanium-oxygen system

Data in the literature on the Magneli oxides of titanium have been critically evaluated and equations have been developed from these data for the standard-state Gibbs energy of formation of the following oxides: Ti₄O₇, Ti₅O₉, Ti₆O₁₁, Ti₈O₁₅, and Ti₉O₁₇. Examination of those data yielded the following:

Phase equilibria in the system Fe-Mo-Cl-H-O

Conclusions Under the conditions we dealt with, only wQstlte is stable in the system Fe-Mo-O while molybdenum is reduced and passes into the solution. Practically with all compositions of the solid solution iron is predominantly chlorinated, and it passes into the molybdenum. Therefore the alloy iron-molybdenum can be obtained through the chloride phase only by chlorination of pure molybdenum. Chlorination of iron oxides and molybdenum oxides in the presence of hydrogen is inefficient because it is difficult to ensure the necessary composition of the gas phase.The results of the present work can be used for working out technological regimes of alloying the surface of iron objects through the chloride phase and for obtaining powdered alloys Iron-molybdenum.Translated from Poroshkovaya Metallurgiya, No. 1(301), pp. 43–46, January, 1988.     

Phase equilibria in the system molybdenum-chromium-carbon

Summary The methods of x-ray diffraction and microstructural analyses were employed for studying the system Mo-Cr-C, and an isothermal section (1350°C) of the system was plotted. At high carbon contents, the alloys which have not been subjected to heat-treatment contain, the-phase, which has a cubic face-centered structure of the NaCl type (a = 4.24–4.27 A). The carbide Mo₂C dissolves up to 46 at.% Cr, and the carbide Cr₂₃C₆ up to 15 at.% Mo. It is shown that the Mo atoms dissolved in the carbide Cr₂₃C₆ are distributed in an ordered manner.     

Phase equilibria in the Co-P-B system

Translated from Poroshkovaya Metallurgiya, No. 5(329), pp. 56–59, May, 1990.     

Phase equilibria in the system zirconium-chromium-carbon

Summary Phase equilibria in the system Zr-Cr-C at 1300°C were investigated by themethods of x-ray diffraction and microstructural analyses (Fig. 2). Zirconium carbide dissolves up to 6 at.% Cr, while chromium carbides dissolve negligible amounts of zirconium. In accordance with results of a thermodynamic calculation, zirconium carbide is in equilibrium with chromium carbides, chromium, and the compound ZrCr₂.