Thermodynamic assessment of the Ga–Sc and Ga–Tb systems

The Ga–Sc and Ga–Tb binary systems have been assessed with CALPHAD method. Liquid is treated as substitutional solution phase, of which the excess Gibbs energies are modeled by Redlich–Kister polynomial function. The binary intermetallic compounds are treated as stoichiometric phases. Thermodynamic parameters of various phases have been optimized and the calculated results are in reasonable agreement with experimental data.     

Thermodynamic modeling of the Ca–Ag binary system

The Ca–Ag binary system has been assessed with CALPHAD approach based on experiment information about phase diagram and thermodynamic properties. The excess Gibbs energies of the solution phases including liquid, bcc and fcc were formulated with Redlich–Kister polynomial functions. The intermetallic compounds Ca₂Ag₉, Ca₂Ag₇, CaAg₂, CaAg, Ca₅Ag₃ and Ca₃Ag were treated as stoichiometric phases. Self-consistent thermodynamic parameters have been obtained and the calculated results agree well with most literature data. Several diagrams and tables concerning the Ca–Ag system are presented.     

Thermodynamic assessment of the Nd–Zn binary system

On the basis of available experimental information, the Nd–Zn binary system has been thermodynamically optimized using the CALPHAD method. The solution phases, liquid, bcc and dhcp, were treated as substitutional solutions, while the intermediate compounds, NdZn, NdZn₂, NdZn₃, Nd₃Zn₁₁, Nd₁₃Zn₅₈, Nd₃Zn₂₂, Nd₂Zn₁₇ and NdZn₁₁, were described as stoichiometric phases. A set of self-consistent parameters formulating the Gibbs energies of various phases in this binary system was obtained. Most of experimental data on thermochemistry and phase diagram reported in the literatures were satisfactorily reproduced.     

Metallic porous materials' design with phase separation in Fe–Cu and Co–Cu systems

The metallic porous materials have been fabricated from the phase separating Fe–Cu and Co–Cu binary alloys on the calculated critical composition by the selective dissolution method. The interconnected phases are observed by electron energy loss spectroscopy mapping in as-melt-spun samples. Because of the difference of electrochemical activity of separated phases, Fe rich, Co rich, and Cu rich phases could be selectively dissolved in nitric acid solution. The fabricated porous sizes were varied widely from a few tens to about a few hundred nanometers depending on the cooling rate difference in as-melt-spun samples.     

First-Principle Calculation Assisted Thermodynamic Assessment of the Pt-Pb System

Thermodynamic assessment of the Pt-Pb binary system has been performed by combining first-principle calculations with the CALPHAD method. The formation enthalpies of the Pt₃Pb and PtPb₄ were calculated by using the projector-augmented-wave (PAW) method within the generalized gradient approximation (GGA). The CALPHAD assessment of the Pt-Pb system was then performed. The solution phases (liquid and fcc) were treated as substitutional solutions, the excess Gibbs energies of which were modeled using the Redlich-Kister polynomial. The three intermetallic compounds, Pt₃Pb, PtPb, and PtPb₄, were described as stoichiometric phases. Thermodynamic parameters of all the phases were optimized, which reproduces the most experimental data.     

Thermodynamic Assessment of the Al-Ba System

The Al-Ba was thermodynamically optimized with the help of CALPHAD method. The solution phases such as liquid, fcc and bcc phases were modeled as substitutional solution phases. The excess Gibbs energies of these phases were treated with Redlich-Kister polynomial functions. A set of self-consistent thermodynamic parameters for describing various phases in the Al-Ba system was obtained, which can well reproduce the corresponding experimental data. The Al-Ba-Ni ternary system were also extrapolated based on the present binary system.     

Thermodynamic assessment of the Mo–Re binary system

The existing Mo–Re phase diagrams are reviewed and a thermodynamic calculation of the Mo–Re binary system is undertaken. The Gibbs energies are estimated for liquid, bcc (Mo), hcp (Re), σ and χ phases. The liquid, bcc (Mo) and hcp (Re) phases are described by a regular solution model, whereas the σ and χ phases are described respectively by three-sublattice models. For the σ phase, two thermodynamic models are used for calculations and the results are compared. The models take into account the crystallographic structure and similarity between the σ and χ phases. The calculated results remove the ambiguity of the existing phase diagram data and are compared with the experimental data in the literature.     

Thermodynamic modeling of the Ru–Zr system

The Ru–Zr system has been critically assessed by means of the CALPHAD technique. Based on the experimental data, the solution phases (liquid, body-centered cubic, hexagonal close-packed) were initially modeled with the Redlich–Kister equation. It was shown that this model had a definite temperature range beyond which the liquid became unstable. To tackle the problem, the solution phases were modeled with a new semi-empirical equation, which was recommended by Kaptay. A two-sublattice model (Ru, Zr)_0.5(Ru, Zr)_0.5 is applied to describe the compound RuZr in order to deal with the order–disorder transition between body-centered cubic solution (A2) and RuZr with CsCl-type structure (B2). Another two-sublattice model (Ru, Zr)_0.6667(Ru, Zr)_0.3333 is applied to describe the compound Ru₂Zr in order to cope with the order–disorder transition between hexagonal close-packed (A3) and Ru₂Zr with MgZn₂-type structure (C14). A set of self-consistent thermodynamic parameters of the Ru–Zr system was obtained.     

Phase equilibria in the Ni–Cr–Ti system at 850°C

The isothermal cross-section through the ternary phase diagram Ni–Cr–Ti at 850°C was constructed by means of diffusion couples and equilibrated alloys. No ternary phases exist in the system at this temperature. The topology of the isotherm is largely determined by the presence of the TiCr₂-Laves phases which are in equilibrium with the binary Ti–Ni intermetallics. About 10 at.% of Ni can be dissolved in the hexagonal β-TiCr₂ at 850°C, and the solubility of nickel in cubic α-TiCr₂ is approximately 4 at.%. A small amount of nickel or chromium increases the stability of the b.c.c. β-Ti structure. At this temperature the β-Ti(Ni)-based solid solution can dissolve up to 18 at.% of Cr.     

Thermodynamic Assessment of Zn-Fe-Nb Ternary System

The Nb-Zn binary system has been thermodynamically assessed using CALPHAD approach by combining available experimental data and the data from ab initio calculations of the formation enthalpies for NbZn₂, NbZn₃ and NbZn₁₅. Solution phases including Liquid, Bcc, Hcp were modeled as substitutional phases, of which the excess Gibbs energies being formulated with the Redlich-Kister polynomial function. All the binary compounds were treated as stoichiometric phases. Incorporated with the reported thermodynamic parameters of Fe-Zn and Fe-Nb binary systems, two isothermal sections at 723 and 873 K of Zn-Fe-Nb ternary system were thermodynamically optimized where one stoichiometric ternary phase (τ) and the ternary solubility in intermetallic compound (ε) were taken into consideration. Furthermore, liquidus projection was predicted accordingly.     

The 260 °C phase equilibria of the Sn–Sb–Ag ternary system and interfacial reactions at the Sn–Sb/Ag joints

The isothermal section of the Sn–Sb–Ag ternary system at 260 °C has been determined in this study by experimental examination. Experimental results show no existence of ternary compounds in the Sn–Sb–Ag system. Two extensive regions of mutual solubility have been determined. The one located between the two binary isomorphous phases, Ag₃Sn and Ag₃Sb, is labeled as and the other one located between the two binary isomorphous phases, Ag₄Sn and Ag₄Sb, is labeled as ξ. The phase is a very stable phase and is in equilibrium with ξ, Sb, SbSn, Sb₂Sn₃, and liquid Sn phases. Each of the Sb and SbSn phases has a limited solubility of Ag. Only one stoichiometric compound, Sb₂Sn₃, exists. Besides phase equilibria determination, the interfacial reactions between the Sn–Sb alloys and the Ag substrate were investigated at 260 °C. It was found that the phase formations in the Sn–Sb/Ag couples are very similar to those in the Sn/Ag couples.     

Prototype calculations of B2 miscibility gaps in ternary b.c.c. systems with strong ordering tendencies

Prototype calculations in ternary ordering systems based on the b.c.c. lattice have been carried out with the Cluster Variation Method (CVM) in the irregular tetrahedron approximation including tetrahedron interactions. The systems under investigations were characterized by strong ordering tendencies (i.e. with large, negative first neighbour interactions in all binary sub-systems) which resulted in the opening of a miscibility gap inside the B2 single-phase field. This miscibility gap is shown to be produced by frustration of the B2 cluster by a calculation using a hypothetical system with identical first neighbour interactions in the three binary sub-systems. This phase diagram presents as a key feature a central three-phase miscibility gap, which transforms into an ordinary two-phase miscibility gap involving two B2 phases after the symmetry of the interactions is broken. The results are discussed in connection with the experimental Fe–Ti–Rh phase diagram.     

Phase formation in rapidly solidified R2T17 intermetallics

Rapid solidification was utilized to produce a series of light and heavy rare earth-transition metal intermetallics in the R_H–Co, R_L–Co/Fe, and Sm–Co(Fe) systems with R_H = Dy and Tb and R_L = Pr and Sm. The influence of Nb–C and Zr–C additions on phase formation in the binary and ternary alloys has also been investigated. The X-ray diffraction patterns obtained with synchrotron radiation were refined by the Rietveld method for structural phase determination and analysis. It was found that the ability to create disorder strongly depended on the rare earth element, with light rare earth systems possessing more disorder, and rapid solidification effectively suppressed the development of long-range order in these compounds. Cobalt in contrast to iron favored the formation of disordered structures. Replacement up to two out of the three of the cobalt atoms with iron in the Sm–Co–Fe system has retained the establishment of the disordered TbCu₇-variant and exhibited complete cobalt–iron solubility. Additions of Nb–C and Zr–C have also greatly influenced the order formation. The comparison of lattice parameters of the intermetallic compounds obtained by rapid solidification to the parameters of equilibrium 2–17 phases summarized in the literature revealed that formation of partially ordered and disordered structures was associated with expansion of the both a- and c-axes in Th₂Zn₁₇- and Th₂Ni₁₇-type phases for all binary compounds.     

Mechanism of Stress Corrosion Cracking of Al–Li Alloys

G.V. Akimov's concepts of the corrosion–electrochemical properties of aluminum alloys containing lithium are developed. It is found that binary Al–Li alloys are insusceptible to stress corrosion cracking, even though their dissolution rate under normal conditions can increase by up to 30 times because of the selective dissolution of lithium. The interaction of dislocations with phases formed upon heat treatments is demonstrated to play a determining role in the stress corrosion cracking of all the basic aluminum–lithium alloys, namely Al–Li, Al–Li–Cu, Al–Li–Cu–Mg, and Al–Li–Mg alloys. The stress corrosion cracking of both binary aluminum–lithium alloys and alloys which are in addition alloyed with copper and magnesium has mainly a dislocation–electrochemical mechanism. The effect of electrochemical factors is well represented by the difference in the magnitude between the pitting initiation potential and the repassivation potential.     

Thermodynamic assessment of the Ti–B system

A consistent thermodynamic data set for the Ti–B system is obtained by means of CALPHAD technology. The sublattice model is used to describe the solid solution phases: (Ti%)₁(B, Va%)_0.5 and (Ti%)₁(B, Va%)₃ for the terminal solution (Ti) and (βTi), and Ti₁(B%, Ti)₁ and (B, Ti%)₁(B%, Ti)₂ for the compound solution TiB and TiB₂, respectively. The intermetallic compound Ti₃B₄ is treated as a stoichiometric compound. The liquid solution phase is assumed to be a substitutional solution with Redlich–Kister formula for the expression of its excess Gibbs energy. The complete T–x phase diagram for the Ti–B binary system is given. The calculation results agree well with experiments.