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The Alloy Phase Diagram International Commission (APDIC) promotes the effective dissemination of data on phase diagrams and thermodynamics of phases in accordance with the required quality standards and furthers the application of phase diagrams in research and industry. The annual report of the Ukrainian Commission on Phase Diagrams and Thermodynamics, which is a member of APDIC as one of the national participants, presents information on the findings of Ukrainian scientists in this field in 2017–2019. Information on the research findings is presented in a table, collecting data on the systems studied and results obtained and listing references to the published papers.

The Mo–Ni–B alloys with a boron content ca.41 at % were prepared by arc melting, annealed at subsolidus temperatures and studied by X-Ray diffraction method, differential thermal analysis and SEM/EPMA microscopy, and the incipient melting temperatures were measured by the Pirani-Alterthum technique. Based on the authors’ experimental data and in view of the data published elsewhere, the partial solidus surface projection has been constructed for the first time for the Mo–Ni–B system in the region Mo–MoB1.0–NiB∼0.8–Ni.

Alloys of the ternary Ni–Ti–Zr system containing 50 to 100 at.% Ni that were annealed at subsolidus temperatures were examined by scanning electron microscopy, electron microprobe analysis, and differential thermal analysis. The solidus surface was constructed in this composition range. A new ternary phase of composition Ni69.2Ti12.5Zr18.3 was found.

The melting diagram and reaction scheme (Scheil diagram) of the Al–Ti–Pt system have been constructed for the first time in the composition range 0–50 at.% Pt using the experimental results for as-cast alloys and alloys annealed at subsolidus temperatures. It is established that ternary compounds τ3, τ4, and τ8 form congruently with participation of the liquid phase and compounds τ1, τ2, τ5, τ6, τ7, τ9, and τ11 by peritectic reactions. All compounds take part in phase equilibria with participation of the liquid phase, forming 31 four-phase and 28 three-phase invariant equilibria at temperatures from 1410 to 660°C.

The liquidus surface of the Al–Ti–Pt system has been constructed for the first time on the composition triangle based on studies of the structure and phase composition and measurement of the liquidus temperatures for the as-cast alloys in the composition range 0–50 at.% Pt produced using a series of techniques. The liquidus surface has 23 primary crystallization fields corresponding to τ1–τ9 and τ11 ternary phases and binary phases formed in the boundary systems and to solid solutions based on components. The extension of these fields and the positions of univariant curves and invariant points have been determined. The liquidus surface exists in the temperature range from 1830°C (corresponding to congruent melting of TiPt compound) to 655°C (temperature of the l ⇄ + eutectic in the binary Al–Pt system).

A series of physicochemical analysis techniques are employed to study the phase equilibria in the aluminum corner of the Al–Ti–Pt system at subsolidus temperatures and in the alloy crystallization process. It has been established for the first time that a ternary τ1 phase (AuCu3 structural type) forms by peritectic reaction L + + ⇄ τ1 at 1405°C. On the solidus surface in the studied composition range at 1405, 1310, 1275, 1060, 925, 820, and 660°C, there are seven isothermal planes that participate in invariant four-phase equilibria involving the liquid phase, three of them being peritectic and the others transitional.

Theoretical bases for the calculation of metastable phase transformations with the participation of supercooled multicomponent melts in the framework of the CALPHAD method are considered. A database with parameters for models of thermodynamic properties of phases in the Cu–Ni–Ti–Zr–Hf system for such calculations is presented. The excess term of the Gibbs energy of liquid alloys is described using the associated solution model, and bcc and fcc solid solutions with a mathematical model with Redlich–Kister polynomials. The diagrams of metastable phase transformations with the participation of supercooled liquid alloys and boundary solid solutions are calculated. The composition ranges for obtaining rapidly quenched and bulk amorphous ternary, quaternary, and quinary alloys of the Cu–Ni–Ti–Zr–Hf system are theoretically assessed.

Optical and scanning electron microscopy, electron microprobe analysis, and X-ray diffraction are employed to examine alloys in the Cu–Ti–Zr ternary system, annealed at 750°C, with copper content from 0 to 50 at.%. A partial isothermal section of the phase diagram is constructed at 750°C in the composition range in question. The existence of a continuous series of solid solutions between CuTi2 and CuZr2 isostructural compounds (γ phase, MoSi2 type) is confirmed. The homogeneity ranges of Cu2TiZr ternary compound (τ1, MgZn2 type) and β-(Ti, Zr), (CuTi) (CuTi type), and CuZr (CsCl type) solid solutions are determined.

Quaternary as-cast Ti 96–x Nb 2 Cr 2 Al x and Ti 93–x Nb 5 Cr 2 Al x alloys, where x = 44, 46, 48, and 50, melted from pure components (~99.9 wt.%) in a laboratory arc furnace, were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), and differential thermal analysis (DTA). Bending testing and fracture toughness measurements were performed at room temperature, and compression testing was carried out in a range from room temperature to 750°C. The alloys were found to consist mainly of a superfine lamellar structure formed during decomposition of hightemperature phases. In addition, the alloys with 50 at.% Al contain grains of the γ phase, and all others have precipitates of the cubic β/β 0 phase at boundaries of the high-temperature phases because of double enrichment of the last melt drops with Cr. The tests show that the Ti 96–x Nb 2 Cr 2 Al x alloys with 46 and 48 at.% Al possess the most balanced properties.

In the present paper, the constituent binary B–Mo system is re-modelled in order to reproduce genuine homogeneity ranges of the molybdenum borides. Based on this, available descriptions of the constituent B–Ti and Mo–Ti systems as well as new experimental data reported in the literature for the ternary B–Mo–Ti system are used to model the B–Mo–Ti system in the entire composition and temperature ranges. The elaborated thermodynamic description is further applied to calculate selected phase equilibria as to provide a comparison between calculated and experimental results. The calculations are shown to reproduce the experimental data reasonably well, however for few alloys belonging to the domain of primary (Ti,Mo)B 2 crystallization the computed solidus temperatures are about 200 K higher than incipient melting temperatures measured by pyrometry.

In the present paper, the ternary Al–Cr–Ti and binary constituent Al–Cr systems are thermodynamically re-modelled based on new experimental information reported in the literature within the past few years. Few key experiments were performed with selected ternary alloys in order to complement data on phase equilibria in the composition range of common TiAl-based alloys. Six sample compositions were prepared and analyzed in the as-cast and annealed conditions by means of SEM/EDS, XRD and DTA techniques. The elaborated thermodynamic description was applied to calculate selected phase equilibria as to provide a comparison between calculated and experimental results. The calculations are shown to reproduce the experimental data reasonably well.

The study confirmed the stability of the previously reported ternary C-phase ( $$Pm\bar{3}$$ , a = 0.77353(3) nm for Al73.5Pt10Ru16.5), whose composition was found to range between Al73Pt6Ru21 and Al73.5Pt14.5Ru12. The thermodynamically stable decagonal phase was revealed for the first time at 700-900 °C in a small compositional region around Al78Pt6Ru16. It belongs to the D4 structural type (1.65 nm periodicity in the specific direction). The metastable Al-Pt χ-phase (P31c) is stabilized by the addition of only ~1.5 at.% Ru and extends up to ~12 at.% Ru. The lattice parameters for Al76Pt18.6Ru5.4 are a = 1.2256(4) and c = 2.7331(4) nm.

Based on novel experimental data the thermodynamic description of the ternary Al–C–Ti system was subject to optimization using the CALPHAD approach (Thermo-Calc/PARROT). The reaction scheme, the projections of the liquidus and solidus surfaces, as well as a number of isothermal sections and isopleths were calculated using the proposed thermodynamic description and compared with the experimental results. The calculations were shown to adequately reproduce the experimental data. The main feature of the phase equilibria in the system is the existence of three ternary compounds P (Ti3AlC), H (Ti2AlC) and N (Ti3AlC2) forming peritectically from the liquid phase and TiC1−x carbide at 1907, 1865 and 2013 K, respectively. It is shown that these three compounds are thermodynamically stable in a wide temperature interval.

As-cast B–Mo–Ti alloys and samples annealed at subsolidus temperatures are experimentally studied by X-ray diffraction and scanning electron microscopy with electron microprobe analysis. Solidus temperatures and temperatures of other phase transformations are measured by differential thermal analysis and pyrometry with the Pirani–Alterthum method. No ternary compounds are found in the examined alloys. Based on the data obtained, the B–Mo–Ti liquidus and solidus surfaces have been constructed for the first time.

The Al–Cr–Fe phase diagram was studied in the compositional range of 50–100 at% Al and partial isothermal sections were determined at 1160, 1100, 1075, 1042, 1000, 900, 800 and 700 °C. In the low-Al part of the studied compositional region the isostructural high-temperature Al–Cr and Al–Fe γ 1 -phases form a continuous region of solid solutions. Both binary Al 13 Fe 4 and Al 5 Fe 2 were found to dissolve up to 6.5 at% Cr while Al 2 Fe was found to extend up to 4.1 at% Cr. The solid solutions based on the Al–Cr γ 2 and μ phases were determined to reach 35.2 and 1.3 at% Fe, respectively. The dissolution of Cr in the Al–Fe binaries only slightly influences their Al concentrations, while the Al–Cr binaries exhibit decreasing Al concentration with increasing Fe concentration. The Al–Cr η -phase dissolves up to 5 at% Fe, which results in a sharp decrease of its Al concentration and increase of melting temperatures. The earlier reported existence of a ternary decagonal D 3 -phase and three complex periodic phases O 1 , H and e was confirmed and their compositions at different temperatures were specified.

International audience; Phase equilibria and phase transformations in the ternary Al-B-Nb system were investigated by XRD, SEM/WDS and SEM/EDS techniques, DTA, and optic pyrometry. No ternary compound, including the ternary phases reported in literature, was found. It was experimentally measured that the Al-Nb phases epsilon (NbAl3), sigma (prototype sigma CrFe) and delta (prototype Cr3Si) have evident ternary extensions with maximal solubility of boron amount to 1.2, 10.4 and 3.2 at.%, respectively. The Al solubility in niobium borides is also significant. The obtained results were used to elaborate the thermodynamic description of this ternary system based on recently published thermodynamic models of the constituent binary subsystems using the CALPHAD approach (Thermo-Calc/PARROT). The Al-B-Nb reaction scheme, projections of the liquidus and solidus surfaces as well as a number of isothermal sections and isopleths were calculated using the proposed thermodynamic description and compared with the experimental results. The calculations were shown to reproduce adequate the experimental data. The main features of the phase equilibria in the range of melting/solidification are the existence of two quasibinary sections, NbAl3-NbB and NbB2-AlB12, eutectic L-E - epsilon + sigma + (NbB) at 1850 K and cascades of invariant U-type reactions.

The solidification of Al–Ti–Pd alloys is studied by light optical and scanning electron microcopy, electron microprobe analysis, X-ray diffraction, and differential thermal analysis in the composition range 0–50 at.% Pd in the Al–AlPd–TiPd–Ti partial system. The liquidus surface projection, melting diagram, and Scheil diagram are constructed for the first time. Eleven regions of primary solidification of ternary compounds, solid solutions based on binary phases, and Ti and Al components are found to exist. The τ3 phase melts congruently while τ1 is formed incongruently. Eleven four-phase invariant equilibria involving a liquid phase exist in the system: two of them are congruent and nine incongruent. The invariant four-phase reactions occur in the temperature range between 630 and 1425–1456°C.

The effect of silicon, germanium, tin (X), and aluminum on the structure, physicochemical and mechanical properties of Ti-B-X and Ti-Al-B (5 and 7.5 at.% B) ternary and Ti-Al-B-X and Ti-Zr-Al-B (9 at.% Al and 5 at.% B; 8.5 at.% Al and 7.5 at.% B) quaternary alloys is studied by metallography, scanning electron microscopy (SEM), X-ray diffraction, differential thermal analysis (DTA), microhardness measurements, Vickers hardness measurements (from room temperature to 900°C), bending tests (room temperature), and compression tests (from room temperature to 700°C). The alloys are melted in an arc furnace from pure materials. Doping with p-elements (Al, Si, Ge, and Sn) does not change the specific titanium-boride eutectic structure in the two-phase (Ti) + TiB field. The doping additions hardly change the chemical composition of the eutectic and only decrease the boron content by 1–2 at.%. The Al, Si, Ge, and Sn (p-elements) are not soluble in TiB titanium borides and completely concentrate in the metal matrix in two-phase (Ti) + TiB alloys. The temperature of incipient sharp softening is shown to be exclusively connected with the matrix composition. It is determined that p-elements increase the hardness and strength of titanium-boride eutectic alloys in the entire temperature range of interest and increase the temperature of incipient sharp softening from 500 to 600-650°C.

The Al–Ti–Pd system has been studied by microstructural analysis, electron microprobe analysis, x-ray diffraction, and differential temperature analysis in the composition range 0–50 at.% Pd (Al–AlPd–TiPd–Ti partial system) at subsolidus temperatures. The solidus surface of the system is constructed for the first time. At subsolidus temperatures, there are two ternary compounds, τ1 (Al61Ti26Pd13, AuCu3 type) and τ3 (Al44Ti35Pd21, MgZn2 type), a continuous solid solution (β0 phase) between isostructural (CsCl type) high-temperature modifications of AlPd and TiPd equiatomic phases, and terminal solid solutions based on β-Ti and α-Ti and TiAl, Ti2Al5, TiAl3, and Al3Pd2 binary compounds and e phase. The above-mentioned phases participate in 11 four-phase invariant equilibria involving the liquid phase and are represented by isothermal tie-line triangles in the temperature range between 630 and 1205°C.

Ternary as-cast Ti55−x Nb x Al45, Ti53−x Nb x Al47, Ti55−x Ta x Al45, and Ti53−x Ta x Al47 alloys, where x = 0, 4, 8, and 12, and Ti45Nb8−x Ta x Al47 and Ti47Nb8−x Ta x Al45 quaternary alloys, where x = 2, 4, and 6, melted in a laboratory arc furnace from pure components (~99.9 wt.%) are studied by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), differential thermal analysis (DTA), and compression testing. The alloys are found to consist mainly of a superfine lamellar structure of decomposition β → α → α + γ → α2 + γ and contain tiny islands of the γ phase and also the β phase at 12 at.% Nb or Ta. The CALPHAD approach is used to obtain a thermodynamic description of the Al − Nb − Ta − Ti system, which adequately reproduces the experimental data. The compression tests performed at room temperature show that the ternary alloys with 45 at.% Al are characterized by higher strength but lower plasticity than the alloys with 47 at.% Al. For the Ti46Nb8Al46 and Ti46Ta8Al46 alloys, high strength in the temperature range 20 – 800°C and a drop in plasticity to 2 – 4% at 200 – 600°C are revealed. Among the quaternary alloys examined, the best combination of strength and plasticity (σ02 = 1043 MPa, σult = 1612 MPa, epl = 12.4%) is exhibited by the Ti47Nb4Ta4Al45 alloy.

12 August 2011 marked the 100th anniversary of Valentin Eremenko’s birth, an academician of the Academy of sciences of the Ukrainian Soviet Republic, an outstanding physical chemist, a founder of the Institute for Problems of Materials Science, National Academy of Sciences of Ukraine. Eremenko’s papers on the physical chemistry of fine particulate systems and surface phenomena, chemical thermodynamics of alloys and metal compounds, and physicochemical analysis of metal and metallic systems have highly been praised by national and international scientific community. Eremenko’s chemical concept of phenomena that occur at interfaces in heterogeneous systems has been brilliantly proven by experiment and widely used in studies focusing on surface phenomena, powder metallurgy processes, compatibility of materials, soldering, etc. The physicochemical constants for simple and complex substances derived from analysis of the phase diagrams and thermodynamic properties of metal, metallic, and semiconductor systems have been included into handbooks and are an important, fundamental component of modern materials science. Eremenko’s scientific ideas and scientific areas are further elaborated by his school of physical chemists.

Partial 1100, 1000, 900 and 700 °C isothermal sections of the Al–Rh–Ru phase diagram were determined. The isostructural binary AlRu and AlRh phases probably form a continuous β-range of the CsCl-type solid solutions. The Al 9 Rh 2 and C-Al 5 Rh 2 dissolve up to 4.5 and 13 at.% Ru, while Al 13 Ru 4 and Al 2 Ru dissolve up to 14.5 and 8 at.% Rh, respectively. A ternary orthorhombic structure ( Pbma , a = 2.34, b = 1.62 and c = 2.00 nm) related to the Al–Rh ɛ-phases was revealed at the extension of the Al–Rh ɛ-phase area at compositions up to Al 77 Rh 15 Ru 8 .

The 1100 °C isothermal section of the Al–Ti–Pt system was experimentally studied in the compositional region below 50 at.% Pt. Most of the binary Al–Ti and Al–Pt intermetallics dissolve about 1.5–3.5 at.% of the third element. Only TiAl and Ti 3 Al contain up to ∼5.5 at.% Pt and Al 2 Pt ∼13 at.% Ti. The Ti 3 Pt, Ti 3 Pt 4 and TiPt phases extend up to 7.5, 9 and 30 at.% Al, respectively. The homogeneity range of the ternary phase τ 1 extends from Al 63.3 Ti 30.6 Pt 6.1 to Al 69.0 Ti 24.2 Pt 6.6 and that of τ 2 from Al 44.1 Ti 34.0 Pt 21.9 to Al 55.1 Ti 20.9 Pt 24.0 . The τ 3 -phase is formed in the compositional region from Al 37 Ti 37.5 Pt 25.5 to Al 42 Ti 32 Pt 26 . Only the Nb(Ir,Al) 2 -type structure of the latter was revealed. The τ 4 -phase exists between Al 31.3 Ti 33.7 Pt 35 and Al 36.6 Ti 29.4 Pt 34 while the τ 5 -phase exists between Al 12.9 Ti 58.9 Pt 28.2 and Al 27.3 Ti 57.3 Pt 15.4 . Apart from these previously reported phases, five new ternary compounds designated τ 6 to τ 10 were revealed. The τ 6 -phase exists between the Al 25.5 Ti 54.2 Pt 20.3 and the Al 30 Ti 54 Pt 16 compositions, and probably has a primitive cubic structure with a = 0.68477(6) nm. The τ 7 -phase was found to be formed around the Al 12 Ti 51 Pt 37 composition, τ 8 , τ 9 and τ 10 -phases exist in the compositional ranges of Al 28.5 Ti 55 Pt 27.5 to Al 33.7 Ti 40 Pt 26.3 , Al 34.5 Ti 48 Pt 17.5 to Al 38 Ti 44 Pt 18 and Al 32.6 Ti 44.3 Pt 23.1 to Al 37.4 Ti 41 Pt 21.6 , respectively.

Based on transmission and scanning electron microscopy, x-ray diffraction, electron microprobe and differential thermal analyses, the solidus surface of the ternary Al–Cr–Fe system is constructed for the first time on the concentration triangle over composition range 58–100 at.% Al. Four ternary compounds, D3, O1, H, and e, with decagonal, orthorhombic base-centered, hexagonal, and orthorhombic primitive lattices participate in phase equilibria on the solidus surface. Solid solutions based on aluminum and binary compounds as well as ternary phases form 12 single-phase surfaces, 25 ruled surfaces of two-phase equilibria bounding two-phase regions, and 14 three-phase isothermal planes corresponding to invariant four-phase equilibria on the solidus surface.

Phase equilibria in the ternary Al–Ti–Pd system have been investigated in the range of the Pd content below 50 at.%. Partial 930 and 1100 °C isothermal sections are constructed. High-temperature bcc solid solution based on β-Ti (A2) widely extends into ternary compositions. With increasing Pd concentration it obeys the CsCl-type ordering (B2) and this high-temperature ordered solid solution links with that between congruent TiPd and AlPd. The Al-rich end of the low-temperature α-Ti region extends up to 6 at.% Pd. The Al–Ti γ-phase and η-phase extend up to 5 at.% Pd. Other binary Al–Ti and Pd–Ti intermetallics dissolve below 3 at.% of the third element. Three ternary compounds τ1, τ2 and τ3 reported earlier were confirmed. The τ1-phase ( P m 3 ¯ m , a = 0.39620 nm) exists in a compositional range between Al60Ti27Pd13 and Al70Ti23Pd7 at 1100 °C and between Al61Ti25Pd14 and Al69Ti24Pd7 at 930 °C. The τ2-phase ( F m 3 ¯ m , a = 1.22589 nm) exists between Al53Ti23Pd24 and Al54Ti21Pd25. The τ3-phase exists in a range between Al42Ti33Pd25 and Al49Ti32Pd19 at 1100 °C and between Al40.5Ti33.5Pd26 and Al48Ti33Pd19 at 930 °C. Apart from the basic structure (P63/mmc, a = 0.51383, c = 0.82438 nm) also a superstructure of the of the Nb(Ir,Al)2-type (P63/mcm, a = 0.89098(11) nm, c = 0.82011(7) nm) was confirmed at the Pd-rich end of this compositional region. According to our preliminary results τ1 melts incongruently at about 1420 °C while τ3 melts congruently at 1295 °C. The τ2-phase is formed in a solid-state reaction between 1050 and 1100 °C.

The Al–Ni–Ir alloy system was studied in the range of above 50 at.% Al. Partial 1150, 1000, 900 and 800 °C isothermal sections were determined. Congruent equiatomic AlIr and AlNi phases form a continuous region of solid solutions. The C–Al 2.7 Ir, χ-Al 28 Ir 9 and Al 9 Ir 2 phases dissolve up to 7, 10.5 and 2.5 at.% Ni, respectively. Increasing the Ni concentration results in a slight decrease of the Al concentration of these phases. The Al 3 Ni 2 phase dissolves up to 2.5 at.% Ir, while the solubility of Ir in Al 3 Ni is 1 at.%. A ternary orthorhombic ɛ 6 -phase ( a = 2.34 nm, b = 1.65 nm, c = 1.24 nm) was found below 1342 °C in a compositional range extending from Al 73 Ni 4 Ir 23 to Al 72 Ni 17.5 Ir 10.5 .

The partial isothermal section at 800°C is represented for the first time. The structure of the Al–Cu–Ir alloys in the Al70Ir30–Al40Cu60–Al range, which are quenched from 800°C, is investigated by SEM/EDX and XRD methods. Three ternary phases (decagonal quasicrystalline D1, orthorhombic e6, and cubic (fcc) C2) are stable at this temperature. The (Al9Ir2), φ, e6, D1, γ1, and є2 phases coexist with a liquid phase at 800°C.

The Al–Cu–Ir alloy system was studied in the compositional region above 30 at.% Al from 1100 to 540 °C. Of the Al–Ir binaries, the β-AlIr, C-Al 2.7 Ir, Al 3 Ir, χ-Al 28 Ir 9 , φ-Al 45 Ir 13 and Al 9 Ir 2 phases dissolve up to 35, 13, 8.5, 4, 3 and 2.5 at.% Cu, respectively. The solubility of Ir in the Al–Cu η 1 (η 2 ), 1 ( 2 ) and θ phases is below 1 at.%, while the γ 0 dissolves up to 4.5 at.% Ir. The equilibria involve four previously reported ternary phases ω, C 2 , ɛ and D 1 forming around Al 70 Cu 20 Ir 10 , Al 63 Cu 13 Ir 24 , Al 72 Cu 9 Ir 19 and Al 60 Cu 24 Ir 16 , respectively, and a new Al 2 CuIr phase revealed inside the β-phase range below 1063 °C. Partial isothermal sections were determined at 1100, 1000, 980, 900, 800, 700, 600 and 540 °C.

The partial mixing enthalpy of nickel in ternary liquid alloys of the Cu–Fe–Ni system is studied by the calorimetric method at 1873 K and xNi = 0–0.55. The $$ \Delta {\overline H_{Ni}} $$ function has mainly negative values over the composition range of interest. The results show the key role of binary interactions in the formation energetics of liquid alloys in the Cu–Fe–Ni system. A set of self-consistent parameters of thermodynamic models of the phases is obtained taking into account experimental data on the thermodynamic properties of liquid and solid solutions and data on stable phase transformations. The thermodynamic assessment of the system is carried out in the framework of the CALPHAD method. The calculated liquidus surface and isothermal and vertical sections of the phase diagram are in satisfactory agreement with corresponding experimental data. The metastable miscibility gap of supercooled liquid alloys in the Cu–Fe–Ni system is calculated.

The thermodynamic description of the ternary system Al–B–Ti is obtained by modelling the Gibbs energy of all individual phases in the system using the CALPHAD approach. The model parameters have been evaluated using the computer optimization technique PARROT based on the available descriptions of the constituent binary systems Al–B, B–Ti and Al–Ti recently published and relevant experimental information on phase equilibria for the ternary system. For the ternary system Al–B–Ti the reaction scheme, projection of the liquidus, solidus and solvus surfaces, selected vertical and isothermal sections are calculated using the proposed thermodynamic description. An acceptable agreement between the calculations and experimental data is achieved.

The thermodynamic description of the entire ternary Al–Nb–Ti system is obtained by CALPHAD modelling of the Gibbs energy of all individual phases, taking into account experimental data on phase equilibria and thermodynamic properties published and complemented by own experiments. The description includes a re-evaluation of the constituent binary Al–Nb system. Selected equilibrium calculations were performed with the Thermo-Calc software using the proposed description. They are shown to well reproduce experimental data on both, phase equilibria and thermodynamic properties in the entire Al–Nb–Ti system.

Partial isothermal sections of the Al–Pd–Ru phase diagram at 790 and 900 °C are presented. Complex orthorhombic ɛ-phases extending from Al3Pd up to 15 at.% Ru exhibit structural variants including transient irregular structures. The Al3Pd2 phase dissolves up to 2 at.% Ru, Al13Ru4

The paper examines alloys in the ternary Al–Cr–Fe system in the region of compositions associated earlier with the extensive region of terminal Fe solid solutions in the hexagonal Al4Cr (μ) binary phase in which iron reaches almost 12 at.%. Scanning electron microscopy, x-ray powder diffraction, and electron diffraction show that the solubility of Fe in the μ-phase is substantially lower. Alloys Al76Cr19Fe5, Al76Cr16Fe8, and Al75Cr16Fe9 annealed at 1000 °C have a complex basecentered orthorhombic structure with a ≈ 3.27 nm, b ≈ 1.24 nm, and c ≈ 2.34 nm.

Partial isothermal sections of the Al–Pd–Ru phase diagram at 1000, 1050 and 1100 °C are presented here. The Al–Pd orthorhombic ɛ-phases dissolve up to ∼15.5 at.% Ru, Al 13 Ru 4 2 Ru up to 1 at.% Pd. Between 66 and 75 at.% Al, ternary quasiperiodic icosahedral phase and three cubic phases: C ( P m 3 ¯ , a = 0.7757 nm), C 1 ( I m 3 ¯ , a = 1.5532 nm) and C 2 ( F m 3 ¯ , a = 1.5566 nm) were revealed. An additional complex cubic structure with a ≈ 3.96 nm was found to be formed at compositions close to those of the icosahedral phase.

The Al–Ir phase diagram was specified in the range between 65 and 90 at.% Al. We confirmed the congruent melting of the Al2.7Ir phase, which forms a eutectic with AlIr. At higher Al concentrations four intermediate phases were found to be formed by a cascade of peritectic reactions: Al3Ir at 1466 °C, Al28Ir9 at 1446 °C, Al45Ir13 at 993 °C and Al9Ir2 at 877 °C. Their structures reported in the literature were confirmed.

Partial 1100, 1000, 900 and 790 °C isothermal sections of the Al–Pd–Ir phase diagram were experimentally determined. The Al–Pd ɛ-phase region extends up to 22 at.% Ir, the Al 4 Pd phase dissolves up to 15.5 at.% Ir and the C–Al 2,7 Ir phase dissolves up to 15 at.% Pd. The Al 9 Ir 2 and Al 28 Ir 9 phases extend up to 2 and 5 at.% Pd, respectively. Two ternary phases were revealed: cubic C 2 ( a = 1.5482(2) nm) and hexagonal C 3 ( a = 1.09135(14), c = 1.3418(9) nm). The isostructural binary AlPd and AlIr phases probably form a continuous β-range of the CsCl-type solid solutions at the temperatures investigated.

The Mo-Ni-B alloys prepared by arc-melting are examined in as-cast and annealed states using x-ray diffraction, scanning electron microscopy with electron probe microanalysis, and differential thermal analysis. The temperatures of invariant equilibria are refined. The projections of liquidus and solidus surfaces are plotted for the Ni-rich region.

The thermodynamic description of the ternary system B–Nb–Ti is obtained by modelling the Gibbs energy of all individual phases in the system using the CALPHAD approach. The model parameters have been evaluated by means of a computer optimization technique based on the available descriptions of the constituent binary systems B–Nb, B–Ti and Nb–Ti and relevant experimental information on phase equilibria for the ternary system. The thermodynamic descriptions of both systems with boron, B–Nb and B–Ti, were published in the first part of the work. For the ternary system B–Nb–Ti several vertical and isothermal sections as well as the projection of the liquidus and solidus surface are calculated using the elaborated thermodynamic description. A tolerable agreement between the calculations and experimental data is achieved.

Phase equilibria in the Ti-TiB2-Ti5Ge3 region of the Ti-Ge-B system are experimentally investigated at melting/solidification temperatures using x-ray diffraction, metallography, EMPA, and differential thermal analysis. The phase diagram is presented as projections of solidus and liquidus surfaces and a vertical section at 7.5 at.% B.

The structure of Ti-Nb-B alloys that are cast and annealed at subsolidus temperatures and at 1400°C is experimentally analyzed (x-ray diffraction, metallography, and electron probe microanalysis), and so are temperatures of their phase transformations (differential thermal analysis and pyrometry). No ternary phases are found in the alloys. Projections of solidus and liquidus surfaces, an isothermal section at 1400°C, and a vertical section at 7.5 at.% B are constructed. A reaction scheme is proposed for alloy crystallization.

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.

Physicochemical analysis methods have been applied to the phase equilibria in the Ti - TiNi - Sc0.53Ni0.47 - Sc subsystem of the Ti - Ni - Sc ternary system. No ternary compounds are found in the subsystem. Isomorphous phases based on Ti2Ni and Sc0.72Ni0.28 form continuous series of solid solutions (η) at subsolidus temperatures, as do the equiatomic compounds TiNi and Sc0.53Ni0.47. The crystallization of the η phase in the ternary system is incongruent, as in the binary systems Ti - Ni and Sc - Ni. The solidus surface for the Ti - TiNi - Sc0.53Ni0.47 - Sc subsystem has a nonvariant four-phase reaction of transition type at 830 °C. The compositions of the alloys that take part in it extend to the Sc - Ni side.

The Al–Pd–Fe decagonal phase with ∼1.6 nm periodicity was found to solidify from the liquid phase in alloys between about 73–82 at% Al and 10–17 at% Pd. Being metastable it is formed at cooling rates as low as 5 °C/min. During TEM experiments the decagonal phase decomposed, depending on composition, into either the multi-twinned orthorhombic e16-phase or the complex nanodomain intermediate state.

The liquidus and solidus surfaces of Al–Pd–Fe were determined between 50 and 100 at.% Al. Fifteen ternary reactions involving the liquid phase were revealed: seven peritectic and eight transition reactions. The lowest temperature of the liquid phase corresponds to the binary Al–Pd eutectic. We also report on the five solid-state four-phase transformations in this compositional range from 750 °C up to subsolidus temperatures.

Scanning and transmission electron microscopy have been used along with x-ray diffraction in the Al - Pd - Fe system to establish a new type of B-centered rhombic N phase. The lattice constants of the N phase are as follows: a = 2.31 nm, b = 1.60 nm, and c = 4.70 nm. Electron-probe microanalysis establishes the composition: Al76.6Pd10.0Fe13.4. Differential thermal analysis indicates that the N phase melts incongruently at a temperature close to 885°C.