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

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.

The Sn–Zr system was re-assessed thermodynamically. Gibbs free energies of the intermetallic compounds of this system were calculated by DFT phonon calculations which can give more reliable information owing to considering the contributions of lattice vibration and electric thermal excitation. Newly published valuable experimental data of liquidus, solidus and invariant reactions of this system were used for the first time in the optimization of the model parameters. It is shown that the previous thermodynamic models, where the Gibbs free energies of formation at different temperatures were replaced by energies of formation at 0 K, overestimated obviously the stability of all the compounds of this system. The thermodynamic model for the Sn–Zr system established in this work would give more solid prediction of phase structures and thermodynamic properties for materials containing Sn–Zr system.

Co–Fe–Ge is an important material system for magnetic and catalyst applications. However, phase equilibria information of the Co–Fe–Ge ternary system is limited. Ternary Co–Fe–Ge alloys equilibrated at 950 °C were prepared. The microstructures, chemical compositions and crystal structure of each phase were determined. The phase equilibria isothermal section at 950 °C of the Co–Fe–Ge ternary system was then proposed. A continuous solid solution phase was formed between the Co₅Ge₃ and Fe₅Ge₃ phases and was labeled the β(Co,Fe)₅Ge₃ phase. There are five three-phase regions in the system at 950 °C. A wide α₂ single-phase, and liquid phase regions with large composition ranges being confirmed at the Ge-poor and Ge-rich sides, respectively.

The partial phase equilibria of the Ni–Al−Dy ternary system have been systematically investigated via experimental analyses and thermodynamic modeling. Using the equilibrated alloy method, the 1150 °C and partial 800 °C isothermal sections of the Ni–Al−Dy ternary system and related Al–Dy binary system were constructed based on scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. Twelve three-phase regions were confirmed and four three-phase equilibria regions were speculated at 1150 °C, eight three-phase regions were determined at 800 °C, and five kinds of primary solidification regions, DyAl₂, τ7, τ5, NiAl and Ni₂Al₃ were observed. A new ternary compound τ12 was discovered, which was stable at 800 °C and disappeared at 1150 °C, the τ1 phase was not stable at 800 and 1150 °C isothermal sections; the ternary compound τ11 was confirmed to be stable at 800 °C. In addition, the primary solidification phases were also identified, and five different primary solidification phases were found. Based on the experimental results available in this study and the literature, the thermodynamic modeling of the Ni–Al–Dy ternary system was obtained using the CALPHAD method. A set of self-consistent thermodynamic parameters for the Ni–Al–Dy ternary system was first obtained with a satisfactory agreement between the experimental and calculated results.

The phase diagram of the Gd-Mn-Ga ternary system is a very important tool for the exploration and development of rare earth Heusler alloys with excellent physical properties, such as magnetic properties, half-metallic properties, ferromagnetic shape memory effect, magnetocaloric effect, ect. In this study, the alloy samples were prepared using a vacuum arc melting furnace, and the 873 K isothermal section of the Gd-Mn-Ga (≤50 at.%Ga) ternary alloy phase diagram was determined by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy spectrometry (EDS). The isothermal section consists of 22 single-phase regions, 44 two-phase regions, and 23 three-phase regions with the presence of 6 ternary compounds, GdMnGa, Gd₂MnGa₆, Gd₂Mn₁₅Ga₂, Gd₂Mn₁₁Ga₆, GdMn_0.56Ga_1.44, and GdMn_0.37Ga_1.63. The solid solubility ranges of Ga in β-Mn and Gd₂Mn₁₅Ga₂ are 5.0–18.1 at.%Ga and 10.5–25.0 at.% Ga. The maximum solid solubility of Ga in α-Mn, GdMn₁₂, and Gd₆Mn₂₃ are 2.0, 2.7, and 7.3 at.% Ga, respectively. The maximum solid solubility of Mn in GdGa₂ is determined to be 13.1 at.% Mn.

Ti–Al–V alloys have received considerable attention owing to their excellent high-temperature mechanical properties. After conducting a critical review of the available experimental data for the ternary Ti–Al–V system, a thermodynamic assessment of the system was carried out over the entire composition and a wide temperature range utilizing the CALPHAD method. The extensive homogeneity ranges of the ${\alpha }_2$ and $\gamma$ phases were satisfactorily reproduced. Of particular significance was the first accurate description of the phase equilibria at 1573 K. The model parameters obtained in this study well represented the thermochemical properties and phase equilibria of the experimental data. Furthermore, the enthalpies of the widely used Ti alloy Ti–6Al–4V were reproduced using the thermodynamic description established in this study. Thus, this study provides a reliable basis for guiding the development and design of Ti–Al–V alloys.