Calphad-computer Coupling of Phase Diagrams and Thermochemistry最新文献

Owing to the low melting temperature and excellent mechanical properties, In is considered a potential low-temperature solder. However, the interfacial reaction between In and Cu substrates is still unclear, specifically regarding the stability of CuIn₂. Although CuIn₂ was often observed at the Cu–In thin film after long-term aging below 100 °C, it is considered as a metastable phase and has not been added into the Cu–In phase diagram yet. In this study, the stability of CuIn₂ and the peritectoid reaction Cu₁₁In₉ + In → CuIn₂ were established using the Cu/In diffusion couple, Cu–In alloy phase equilibria, and decomposition investigation of CuIn₂. The peritectoid temperature was determined to be in the range of 110–105 °C. Finally, thermodynamic assessment was conducted based on the experimental data and the revised Cu–In phase diagram.

Diffusion coefficients in the BCC phase of the Al–Nb–V ternary system are studied for the first time, including an assessment of the atomic mobilities. Ternary interdiffusion coefficients are obtained from the intersecting diffusion paths of several sets of diffusion couples that are annealed at both 1100 °C and 1200 °C. Existing experimental data from the pertinent binary systems are also employed for the assessments of atomic mobilities using the 1-parameter Z-Z-Z binary diffusion coefficient model developed by Zhong et al [1]. Interdiffusion coefficients in the BCC region of the Al–V system are also extracted through a forward-simulation analysis and incorporated into the mobility modeling. A complete description of diffusion in the BCC phase of the Al–Nb–V system is presented following the Binary and Cross-Binary Parameters Only (BCBPO) model developed by Zhong and Zhao [2]. Our data will be valuable input to diffusion-related simulation of refractory high entropy alloys containing aluminum.

Establishing a Ni–Ti–V system diffusion kinetics database contributes to a better understanding of the precipitation processes in shape memory alloys. In this paper, eleven sets of BCC_B2 Ni–Ti–V single-phase diffusion couples were prepared and annealed at temperatures of 1223 K, 1273 K, and 1323 K. The composition-distance curves were determined using the electron probe microstructure analysis technique. The interdiffusion coefficients were extracted using the HitDIC software, which is based on the numerical inverse method. The software demonstrated high accuracy in predicting the composition curves of the prepared diffusion couples. The interdiffusion coefficients inferred from the HitDIC software and the ones calculated by the Matano-Kirkaldy method achieved good agreement. This demonstrates the reliability and rationality of the evaluated interdiffusion coefficients. This study also investigated the composition and temperature dependencies of interdiffusion coefficients.

The selective crystallization and phase separation process has been regarded as a promising process for the recycling of titanium from titania-bearing furnace slag, however, the composition modification mechanism still remains unclear due to the lack of fundamental thermodynamic data. In the present work, the influence of ZrO₂ addition on the equilibrium phase relations and the 1400 °C isotherm for CaO-SiO₂-TiO₂ system were experimentally determined by using the high temperature equilibration-quenching technique, and Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry, and X-ray diffraction analysis. The equilibrium solid phases of rutile (TiO₂), perovskite (CaTiO₃), and tridymite (SiO₂) are determined to be coexisting with the liquid phase. In addition, comparisons of present results with thermodynamic calculation by FactSage show significant discrepancies. The present work is important for enriching the thermodynamic database of titania-bearing slag oxide systems as well as optimizing the selective crystallization and phase separation process.

Accounting for the elusive gas phase in thermodynamic equilibrium calculations is demonstrated to be important for achieving accurate and unique determination of constituent element chemical potentials, when Gibbs energy minimization (GEM) encounter indeterminacy due to rank deficiency in mass-balance equations. The molar GEM of the equilibrium vapor phase offers a robust solution for unambiguously and accurately determining element chemical potentials. To enable this, a novel optimization method for mass-balance equation is presented, paving the way for reliable thermodynamic calculations.

This paper presents the results of our comprehensive study of phase equilibria in the Al–Fe–Mo system using DTA, X-ray diffraction, SEM and electron probe microanalysis. The liquidus and solidus projections were constructed. It is shown that the ternary compound Al₈FeMo₃ (τ) melts congruently at >1500 °C and has a homogeneity range from 2 to 9 at.% Fe and from 23.5 to 25 at.% Mo. Isostructural phases (Mo), (αFe) and AlMo (W-type structure, cI2-Im-3m) at solidus temperatures form a continuous solid solution (αFe,Mo,AlMo). Unlike the AlMo binary phase, which is not retained by quenching, the ternary (αFe,Mo,AlMo) phase is easily quenched due to its lower decomposition temperature. Among the binary based phases, the Al₈Fe₅ (ε) phase has the widest homogeneity region, which extends up to 24 at.% Mo at solidus temperatures. It is shown that the addition of Mo stabilizes the Al₈Fe₅ (ε) phase, and the temperature of its formation in the ternary system increases to 1331 °C in contrast to 1234 °C in the binary. Moreover, according to XRD data, the Al₈Fe₅ (ε) phase in the ternary system has a rhombohedral structure of the Al₈Cr₅-type (hR78-R-3m), rather than cubic Cu₅Zn₈-type structure (cI52-I-43m), like the binary one. A new binary compound Al₄₅Mo₇ was identified for the first time. Its crystal structure is established as monoclinic Al₄₅V₇-type (mS104-C2/m) with the lattice parameters a = 20.534, b = 7.561, c = 10.910 Å, β = 107.33. It was shown to form by peritectic reaction L + Al₅Mo ⇄ Al₄₅Mo₇ at ∼800 °C. Iron additions stabilize the Al₄Mo phase, which in the binary system is stable above 942 °C.

38 annealed and 30 as-cast alloys were investigated to construct the isothermal sections at 1273 and 1473 K and the liquidus surface projection of the Co–Mo–Ta system by SEM/EDS and XRD methods. The three-phase regions Co₃Mo+λ₃+μ and fcc(Co) + Co₃Mo+λ₃ at 1273 K, and the three-phase region fcc(Co)+λ₃+μ at 1473 K, were determined. In the liquidus surface projection, eight primary solidification phase regions, fcc(Co), bcc(Mo, Ta), σ, μ, λ₁, λ₂, λ₃ and CoTa₂, and five invariant reactions, liq.→fcc(Co)+λ₃+μ, liq.→λ₁+λ₃+μ, liq.+λ₂→λ₁+λ₃, liq.+CoTa₂→μ+bcc(Mo, Ta) and liq.+bcc(Mo, Ta)+σ→μ, were obtained. On the basis of the experimental results, the Co–Mo–Ta system was evaluated to obtain a set of self-consistent thermodynamic parameters by CALPHAD method.

The thermodynamic evaluation of the Er–Sc binary system was performed using the Calphad method, computing thermodynamic parameters for the Liquid phase, Hcp phase, and Bcc phase. The calculated results align well with existing experimental phase diagrams. Furthermore, by employing electron probe microanalysis and X-ray diffraction testing, the phase equilibria for the Al–Er-Sc ternary system at 600 °C were determined. Experimental findings indicated that both Al–Er and Al–Sc binary systems exhibit some solubility for the third component when extended to the ternary system. Leveraging thermodynamic parameters from the literature for Al–Er and Al–Sc binary system and those calculated for the Er–Sc binary system in this work, a comprehensive thermodynamic evaluation of the Al–Er-Sc ternary system is carried out. The computed results exhibit good agreement with the experimental data, providing consistent and reasonable thermodynamic parameters for the isothermal and vertical sections.

In the present work, the first-principles calculations were performed to study the enthalpies of mixing and the magnetic moments of the solid solutions in the Ni–Re and Co–Re systems. Meanwhile, the phase equilibria of the binary Ni–Re, Co–Re and ternary Ni–Co-Re alloys were investigated using equilibrated alloys and diffusion couples. Various types of data from the present work as well as the literature were used to perform a thermodynamic assessment of the ternary Ni–Co-Re and sub-binary systems using the CALPHAD method. Based on the present thermodynamic parameters, the atomic mobilities for the fcc phase in the Ni–Re and Co–Re systems were reassessed to reproduce experimental data in the literature. Furthermore, several ternary Ni–Co-Re diffusion couples were assembled and annealed at 1273 K and 1473 K to deduce the interdiffusion coefficients. On the basis of diffusion experimental data from the present work and the literature, atomic mobilities of Ni, Co, and Re in the fcc Ni–Co-Re system were assessed coupled with the present thermodynamic description. The accuracy of the assessed atomic mobilities was confirmed by comparing with the experimental interdiffusion coefficients, composition profiles and diffusion paths.

A thermodynamic evaluation of the Cr–Si system was performed concerning the latest experimental phase diagram and with the aid of first-principles calculations. The thermodynamic parameters for the Gibbs energy of pure Cr were modified based on the new experimental value of 1861 °C for the melting point of pure Cr, which was previously reported as 1907 °C in the SGTE database. The Gibbs energy descriptions of the Cr₃Si and Cr₅Si₃ phases were revised using Cr₃(Cr,Si)- and (Cr,Si)₅Si₃-type two-sublattice models to reproduce the latest experimental results of their solubility composition ranges, that is, Cr₃Si extending toward the Cr-rich side and Cr₅Si₃ extending toward the Si-rich side from the stoichiometry. The CrSi and CrSi₂ phases were considered line compounds with no solubility range, and the solubility of Cr in the Si phase was ignored. A set of self-consistent thermodynamic parameters for the Cr–Si system was obtained using the CALPHAD technique. The phase diagrams calculated using the optimized parameters showed reasonable agreement with the latest phase equilibrium data and thermodynamic property data in the literature, including the enthalpy of mixing, formation enthalpy, and chemical potential diagrams of Cr and Si in the equilibrium phases.