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The isothermal sections of the Co–Ni–Ti system at 950 and 1 000 °C were investigated experimentally. Diffusion couples were measured by electron probe microanalysis to construct the phase relations at 950 °C, whereas eleven key alloys annealed at 1 000 °C were investigated using X-ray diffraction and electron probe microanalysis. The ternary phase, τ-(Co,Ni)3Ti (hP24-VCo3), was observed at both temperatures. At 950 °C, continuous solid solutions are formed between CoTi2 and NiTi2 as well as between CoTi and NiTi. Eight 3-phase regions, i. e. Ni3Ti + (Co,Ni)Ti + τ, Ni3Ti + γ-(Co,Ni) + τ, τ + c-Co2Ti + (Co,Ni)Ti, τ + c-Co2Ti + Co3Ti, τ + Co3Ti + γ-(Co,Ni), c-Co2Ti + h-Co2Ti + Co3Ti, L + β-(Ti) + (Co,Ni)Ti2 and L + (Co,Ni)Ti2 + (Co,Ni)Ti, were constructed at 1 000 °C. Considerable ternary solubilities in Ni3Ti, Co3Ti and c-Co2Ti were determined.

The interdiffusion behavior of bcc_B2 Ni–Al–Cu alloys at 1173 K was experimentally investigated on the basis of six groups of bulk diffusion couples. With the electron probe microanalysis technique and the Matano–Kirkaldy method, the composition-dependent mole-fraction interdiffusion coefficients and the interdiffusion fluxes in bcc_B2 Ni–Al–Cu alloys at 1173 K were determined. The reliability of the presently obtained interdiffusivities was verified by the thermodynamic stability constraints, comparison with the interdiffusion coefficients in boundary binary bcc_B2 Ni–Al alloys as well as numerical simulations based on Fick's second law.

An atomic mobility database for binary disordered and ordered fcc phases in multicomponent Al-Cu-Fe–Mg-Mn–Ni–Si–Zn alloys was established based on a critical review of diffusion data in various constituent binary systems via the DICTRA (DIffusion Controlled TRAnsformation) software package. The mobility parameters for self-diffusion in the metastable fcc structure were determined through a semi-empirical method. An effective strategy, which takes the homogeneity range and defect concentration into account, was used to optimize the atomic mobilities of L12 phase in the Fe–Ni system. Comprehensive comparisons between various calculated and measured diffusivities show that most of the experimental data can be well reproduced by the presently obtained atomic mobilities. The general agreement between the model-predicted concentration profiles and the experimental ones in the Al-Ni–Si, Al-Mg-Zn and Cu-Mn–Ni–Zn diffusion couples validates the potential application of the present atomic mobility database to predict the concentration profiles in higher order systems. An 8-elemental diffusion couple was also simulated with the present database.

Phase equilibria of the Gd–Ni binary and Mg–Ni–Gd ternary systems were critically investigated using equilibrated alloys and differential scanning calorimeter measurements. The phase diagram of the Gd–Ni binary system was updated from scanning electron microscopy with energy-dispersive X-ray spectrometry, X-ray diffraction, and differential scanning calorimeter results obtained on binary samples over the entire composition range. Major changes made in the present work include the absence of the Gd3Ni2 and GdNi4 compounds and the congruent melting point of the GdNi compound. An isothermal section of the Mg–Ni–Gd ternary system at 673 K was constructed from the investigations on 22 ternary alloys. In total, six ternary compounds were identified in this work, three of which were observed to crystallize in the Cu4MgSn (τ1), Mo2FeB2 (τ2), and Ru4Al3B2-type (τ3) structures, respectively. As in most of the Mg–rare-earth metal–transition metal ternary systems, a long-period-stacking ordered phase was identified to have an 18R structure and a melting temperature of 806 K. Noticeable solid solubility of Ni in the Mg5Gd and Mg3Gd binary compounds was observed.

First-principles calculations of the total energy and elastic properties of the L12-based Al3RE (RE = Sc, Y, Lanthanide) at T = 0 K are performed by using the projector augmented-wave method within the generalized gradient approximation. The lattice constants, formation enthalpies, elastic constants and bulk modulus of the L12-based Al3RE are obtained. Young's modulus, shear modulus and Poisson's ratios are also estimated in the present work. By using the Debye – Grüneisen model, the Debye temperatures, Grüneisen constants and the sound velocity are obtained for the L12-based Al3RE. All the calculated results are in good agreement with experimental values and other theoretical calculations available.

The phase equilibria of the Co–Cu –Ti system at 850 °C are investigated using a high-efficiency diffusion couple and six key ternary alloys. The samples are examined by means of optical microscopy, scanning electron microscopy, and electron probe microanalysis. At 850 °C, no ternary compound is found. The Ti3Cu phase is a metastable phase. The solubilities of Cu in Ti2Co, TiCo, TiCo2(c) and TiCo3 were determined to be 8.7, 35.8, 2.1, and 5.4 at.%, respectively. And the solubilities of Co in Ti2Cu, TiCu, Ti3Cu4, and TiCu2 were measured to be 6.6, 0.7, 2.4, and 10.2 at.%, respectively. The following 9 three-phase equilibria are observed: (Ti) + Ti2Co + Ti2Cu, Ti2Co + Ti2Cu + TiCo, Ti2Cu + TiCu + TiCo, TiCu + Ti3Cu4 + TiCo, Ti3Cu4 + TiCu2 + TiCo, TiCu2 + TiCo + (Cu), TiCo + TiCo2(c) + (Cu), TiCo2(h) + TiCo3 + (Cu), and TiCo3 + (Co) + (Cu).

The phase equilibria of the Co–Cu–Ti system at 850°C are investigated using a high-efficiency diffusion couple and six key ternary alloys. The samples are examined by means of optical microscopy, scanning electron microscopy, and electron probe microanalysis. At 850°C, no ternary compound is found. The Ti3Cu phase is a metastable phase. The solubilities of Cu in Ti2Co, TiCo, TiCo2(c) and TiCo3 were determined to be 8.7, 35.8, 2.1, and 5.4 at.%, respectively. And the solubilities of Co in Ti2Cu, TiCu, Ti3Cu4, and TiCu2 were measured to be 6.6, 0.7, 2.4, and 10.2 at.%, respectively. The following 9 three-phase equilibria are observed: (Ti) + Ti2Co + Ti2Cu, Ti2Co + Ti2Cu + TiCo, Ti2Cu + TiCu + TiCo, TiCu + Ti3Cu4 + TiCo, Ti3Cu4 + TiCu2 + TiCo, TiCu2 + TiCo + (Cu), TiCo + TiCo2(c) + (Cu), TiCo2(h) + TiCo3 + (Cu), and TiCo3 + (Co) + (Cu).

The SrO–B2O3 pseudo-binary system has been assessed. The liquid phase is described by means of a two-sublattice ionic solution model, (Sr+2)P(O–2, BO3–3, B4O7–2, B3O4.5)Q, where P and Q are constant. All the solid phases are treated as stoichiometric compounds. A set of self-consistent parameters is obtained by using the CALPHAD technique. A comparison between the calculated results and experimental data from literature is presented. It is found that the former reproduce the latter very well on both aspects of phase diagram and thermodynamic properties.

A thermodynamic assessment of the Au–Al system has been performed by using the CALPHAD method. The excess Gibbs energies of the solution phases were formulated with a Redlich – Kister expression, while the other intermetallic phases were described as stoichiometric compounds because of their limited composition ranges. Based on the experimental informations on the phase diagram and the thermodynamics, the thermodynamic parameters of all phases in this system have been optimized.

The B–Co system is investigated via thermodynamic modeling and experiments. In the modeling section, all of the experimental phase diagram and thermodynamic data available from the literature were critically reviewed and assessed by using thermodynamic models for the Gibbs energies of individual phases. In the experimental section, 6 key alloys were prepared by arc melting Co slug and B pieces and annealing at 900 °C for 9 days. Water-quenched samples were analysed by using X-ray diffraction, optical microscopy, electron probe microanalysis and differential thermal analysis techniques. The measured invariant reaction temperatures are: 1136 ± 2 °C for Liquid (L) ↔ (αCo) + Co3B, 1157 ± 2 °C for L + Co2B ↔ Co3B, 1263 ± 2 °C for L ↔ Co2B + CoB, and 1358 ± 2 °C for L ↔ CoB + B. A consistent thermodynamic data set for the B–Co system is finally obtained by considering the present experimental results and reliable literature data. Comparisons between the calculated and measured phase diagram and thermodynamic quantities show that all of the accurate experimental information is satisfactorily accounted for by the thermodynamic description.

Characteristics which can be used to determine the type of invariant reactions in the multicomponent system have been discussed. They are: (i) the relations among solidus temperatures; (ii) the position of the liquid phase; (iii) the phase present after incipient melting: the number of univariant phase regions can be observed in partially melting samples or the solid phases which can occur in partially melting samples which originally consist of other solid phases. Several aspects which must be considered in using the above principles: the sensitivity and accuracy of experimental methods; the solubility of solid phases; the consistence among invariant reactions are also discussed. An example of using these principles in determination of the invariant reactions in the vicinity of the (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O 10-x (2223) phase in the Bi(Pb)SrCaCuO system is given.