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

MnCr₂O₄, known for its unique structure and properties, finds wide applications in catalysts, magnetic materials, electrode materials, and other fields. In this study, high-purity MnCr₂O₄ samples were synthesized via the liquid-phase combustion method and characterized. Thermodynamic data within the temperature range of 350–1350 K was predicted using NKR, and experimental thermodynamic data within the temperature ranges of 15–300 K and 623–1273 K were determined using a PPMS and drop calorimeter. Based on this data, the heat capacity as a function of temperature for MnCr₂O₄ was calculated: $C_p=161.0157+0.01864T-1589402.7435T^{-2}\left(J/\text{mol}·K\right)\left(623\sim 1273K\right)$, along with the enthalpy change, entropy change, and Gibbs energy change in the temperature range of 300∼1250 K. Thermodynamic analysis of the synthesis of MnCr₂O₄ in the field of materials and its treatment in metallurgy using experimental and computational results. This study addresses the thermodynamic knowledge gaps of MnCr₂O₄ and provides a valuable reference for its application in production practice.

The development of conductive materials plays a crucial role in improving the efficiency of electrochemical processes. In polycrystalline materials, space charge layers (SCLs) adjacent to grain boundaries (GBs) often dictate charge transport behavior. This study explores relaxing the charge neutrality constraint in the CALculation of PHAse Diagrams (CALPHAD) approach as a new method to model the electrical conductivity effects of SCLs. A new charge-dependent defect chemistry analysis is applied to the wustite, magnetite, and hematite phases in the Fe–O binary system. Using pycalphad, charge-dependent results for the molar Gibbs energies, Brouwer diagrams, and charge carrier concentrations were determined for each phase at 1273K within the oxygen partial pressure stability ranges. With a negative charge of 0.16 × 10⁻¹⁹ C, the hematite and magnetite phases exhibit an increased charge carrier concentration. The opposite trend was observed for wustite. While further work is needed to quantify the electrical conductivity effects of the SCLs and GBs with this approach, it provides a robust thermodynamic foundation to rapidly develop and optimize conductive materials.

We conducted ab initio molecular dynamics simulations to systematically examine the composition-dependent thermodynamic properties and atomic-scale interactions in liquid Ti–Al–Ni alloys throughout the entire ternary phase space at 2033 K. The calculated enthalpies of mixing demonstrated exothermic tendencies, with a distinct minimum in the composition of Ti_0.0Al_0.50Ni_0.50, indicating significant Al–Ni attractive interactions. Incorporating ternary interaction parameters into the Redlich-Kister-Muggianu equation enabled accurate modeling of the complex variations in mixing enthalpy. Analysis of partial pair correlation functions and structure factors revealed chemical and topological short-range ordering (SRO), as well as medium-range ordering, within the liquid alloy. Quantifying deviations from ideal configurational entropy clarifies the coupling between chemical SRO and topological SRO, significantly impacting the overall Gibbs energy of mixing. This comprehensive atomistic study provides insights into the thermodynamics of Ti–Al–Ni alloys, paving the way for tailoring their properties for high-performance applications.

Based on experimental data measured by scanning electron microscope (SEM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA), isothermal sections of Ti–Mo-Hf system at 800 °C and 1000 °C were constructed. Four and three three-phase regions were derived in the isothermal sections at 800 and 1000 °C, respectively. In addition, a new ternary compound named τ was discovered. The maximum solubilities of the three elements, Ti, Mo and Hf in τ were measured at 800 °C and 1000 °C. At the same time, the solid solubilities of Ti in HfMo₂_C15 and Mo in Hcp were also obtained. According to the measured experimental data, the Ti–Mo-Hf system was optimized using the CALPHAD (CALculation of PHAse Diagrams) method. The solution phases, liquid, Bcc and Hcp, were treated as substitutional solution, while the intermetallic compounds were modeled using sublattice models. HfMo₂_C15 was treated as (Hf, Mo, Ti)₁(Hf, Mo, Ti)₂. The ternary phase τ was considered as a stoichiometric compound and its thermodynamic modeling was defined as (Ti)₃(Mo)₃₍Hf)₁₄. The calculated results showed good agreement with the experimental phase equilibrium data, leading to the derivation of a set of self-consistent thermodynamic parameters for the Ti–Mo-Hf system.

Property models are becoming more widely adopted by commercial Calphad databases, but they are not nearly as common in non-commercial or traditional academic Calphad databases. A primary driver is that user-friendly Calphad modeling tools that support property models are not widely available. Here we present new property modeling capabilities that have been implemented in ESPEI (the Extensible, Self-optimizing Phase Equilibrium Infrastructure). These capabilities include both generating property model parameters from data and improvements to the algorithmic selection of the most appropriate model from a series of candidates. Two illustrative examples are given that use ESPEI to fit different property models. First, we generate molar volume model parameters for Group IV, V, and VI refractory BCC alloys based on the model by Lu et al. (2005). Second, we demonstrate the extensibility of ESPEI’s property modeling capabilities by implementing a custom PyCalphad model for BCC elastic stiffness parameters to generate and compare parameters to the ones assessed by Marker et al. (2018) using the same data. Property models generated by ESPEI can be used in PyCalphad or further optimized with uncertainty quantification using ESPEI.

An integrated modeling framework (PanPhaseField) has been developed, which enables a direct and fast coupling between CALPHAD calculations and large-scale phase field simulations for multi-component alloys. It adopts an open architecture allowing for integration of user-defined phase field models in a plug-and-play manner by taking full advantage of the user-friendly graphical interface of Pandat software. The developed modeling platform becomes an enabling tool that can be used to simulate the evolution of spatially varying microstructures of industrial complex alloys for various engineering applications.

Through the integration of experimental investigations and thermodynamic modeling, a thorough exploration of the phase equilibria in the Ni–Zr–Y ternary system was undertaken. Twenty-six ternary alloys were meticulously prepared to study the isothermal sections at 500 and 700 °C, employing techniques such as X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS). The solubilities of Zr in the Ni–Y binary compounds and Y in the Ni–Zr binary compounds were measured. A ternary compound named τ (Ni₂(Y, Zr)) was confirmed at 700 °C. Utilizing thermodynamic parameters of three binary systems and available experimental phase equilibria data from literature and this work, a thermodynamic assessment of the Ni–Zr–Y system was conducted using the CALPHAD (CALculation of PHAse Diagrams) approach. A set of thermodynamic parameters was obtained and the isothermal sections at 500, 597 and 700 °C were calculated, and the calculated results demonstrated a strong agreement with experimental data. The liquidus projection and reaction scheme of the Ni–Zr–Y system was predicted. This work can be used as a basis for the multicomponent thermodynamic database of Ni-based alloys.

This work examines the thermochemistry of the chromium difluoride CrF${}_2$ corrosion product in the molten

In the present work the phase equilibria in a system of zirconium and hafnium dioxides and europium sesquioxide have been studied. The study was conducted at temperatures of 1700 °С and 1500 °С. Based on the results, isothermal sections at these temperatures were constructed. It was found that in the ZrО₂–HfO₂–Eu₂O₃ ternary system at temperatures of 1700 °С and 1500 °С solid solutions are formed on a monoclinic (M, space group P2₁/C) modification of HfO₂, a tetragonal (T, space group P4₂/nmc) modification of ZrO₂, cubic solid solutions ZrO₂ (HfO₂) with a fluorite structure (F, space group Fm3m), C-type cubic solid solutions of Eu₂O₃ (space group Ia-3), solid solutions based on the monoclinic modification (B, space group C2/m) of Eu₂O₃, as well as an ordered phase with a pyrochlore structure of Eu₂Zr₂O₇ (Eu₂Hf₂O₇) (Py, space group Fd-3m). The phase boundaries and the unit cell parameters of the formed phases were determined. The studied isothermal sections of the ZrО₂–HfO₂–Eu₂O₃ system are characterized by the formation of continuous series of cubic solid solutions based on the phase with a pyrochlore structure. The formation of new phases in the ZrО₂–HfO₂–Eu₂O₃ system at 1700 °С and 1500 °С was not observed.

Ag–Se and Ag–Pb–Se are important material systems for thermoelectric applications, yet their phase equilibria and thermodynamic descriptions have not been studied extensively. This study experimentally determines the phase equilibria of isothermal sections at 550°C and 400°C. No ternary compound is found, and the third element's solubility in the binary compounds is negligible. The Ag–Se binary system is thermodynamically modeled using the Calphad method. Based on the experimental results in this work and those from the literature review. This study proposes the thermodynamic descriptions of the Ag–Pb–Se ternary system using the Calphad method for the first time. The isothermal sections, isopleth sections, and liquidus projection were calculated and compared with the experimental data, showing good agreement between the experimental results and thermodynamic calculation.