Journal of Phase Equilibria and Diffusion最新文献

The phase equilibria of the Er-Al-Zr ternary system at 500 °C were investigated using a combination of electron probe microanalyzer and x-ray diffraction. The microstructure and diffraction peaks were analyzed to determine the phases and compositions of Er-Al-Zr ternary system. Based on the experimental results, the isothermal phase diagram of the Er-Al-Zr ternary system consists of 14 three-phase equilibrium regions, 15 two-phase equilibrium regions, and 13 stable binary compounds, but no ternary compounds were detected. The solubility of Er in the Al₂Zr, Al₃Zr₂, AlZr, Al₃Zr_4, Al₂Zr₃ is 9.9, 5.3, 9.0, 12.4, 6.7 at.%, respectively. The present work could be important for alloy design of Al-based alloys and thermodynamic analysis of the Er-Al-Zr ternary system.

Phases and equilibria involved in the isothermal section at 500 °C of the ternary Al-Fe-Pr system have been here investigated in the whole composition range by means of X-ray diffraction, optical and scanning electron microscopy, and electron probe microanalysis. Phase equilibria are characterised by the formation of two binary solid solutions, Pr₂(Fe_xAl_1−x)₁₇ with 0.34 ≤ x ≤ 1.00 (hR57–Th₂Zn₁₇) and Pr(Fe_xAl_1−x)₂ with 0 ≤ x ≤ 0.20 (cF24–Cu₂Mg), and four ternary compounds, τ₁-PrFe₂Al₁₀ (oS52-YbFe₂Al₁₀), τ₂-PrFe₂Al₈ (oP44-CeFe₂Al₈), τ₃-Pr(Fe_xAl_1−x)₁₂ with 0.28 ≤ x ≤ 0.44 (tI26-ThMn₁₂) and τ₄-Pr₆(Fe_xAl_1−x)₁₄ with 0.63 ≤ x ≤ 0.81 (tI80-La₆Co₁₁Ga₃), which have been confirmed. The solid solubility ranges of the binary and ternary compounds have been considered and trends of their lattice parameters studied. The complete isothermal section has been obtained and the general features of the section are discussed and compared with those of other ternary systems of light R (La, Ce, Pr, Nd, Sm) with Al and Fe.

A thermodynamic description of the Ti-Al-Fe system was established with reassessed Ti-Al and Ti-Fe binary systems using density function theory (DFT) data. All stable and metastable end members of BCC_B2, BCC_D0₃/B32, BCC_L2₁, inverse BCC_L2₁, Laves C14, D0₁₉-Ti₃Al, L1₀-TiAl, Ti Al₂, Ti₃Al₅, D0₂₂-TiAl₃, τ₂ and τ₃ in the Ti-Al, Ti-Fe and Ti-Al-Fe systems were energetically defined with available experimental data and DFT calculations, reaching reasonable consistency. The ternary description was used to successfully calculate the A2-B2-L2₁ transformation in Fe-rich corner and A2-B2 transformation in Ti-rich corner, allowing the design of Ti-rich and Fe-rich alloys in this system.

The microstructures and properties of foundry alloys designated by the generic term “cast irons” are highly diverse, even if we limit ourselves to so-called silicon cast irons, which are essentially quasi-eutectic Fe-C-Si alloys. This diversity is compounded by the fact that these microstructures appear partly during solidification and partly during solid-state transformations. Throughout the scientific career of Mats Hillert, his attention has been drawn to the wide range of phenomena involved in the formation of cast iron microstructures during solidification, as the present review of his contributions in this field shows. In addition, much of his work on the solid-state transformations of steels has found—or should find—an echo in the description of the matrix microstructure of graphitic cast irons, which is the subject of the final part of this article.

Reliable thermodynamic and kinetic databases are essential for designing and developing novel magnesium (Mg) alloys for elevated-temperature applications in the automotive and aerospace industries. This study investigated diffusion behaviors of HCP Mg-Ag-Sn alloys by four sets of three diffusion couples annealed at 450, 500, and 550 °C, respectively. Interdiffusion and impurity diffusion coefficients at the three annealing temperatures were extracted using the forward-simulation method. The determined diffusion coefficients, combined with prior results in the literature, were then used to assess atomic mobilities for the HCP phase of the Mg-Ag-Sn system. This assessment was conducted using the DICTRA and the TCMG5 thermodynamic database within the Thermo-Calc software. Comprehensive comparisons between calculated and experimental diffusion coefficients yielded an excellent agreement. The atomic mobilities were also further validated by appropriate predictions of concentration profiles and diffusion paths observed in independent diffusion couple experiments performed at 525 °C for 18 hrs. It has been found that the addition of Sn and Ag both increase the diffusivity of Ag in HCP Mg and Sn in HCP Mg in the stable temperature range of HCP Mg, respectively. This improved understanding of the kinetics in the Mg-Ag-Sn ternary system is essential for controlling diffusion-dependent properties such as coarsening and, therefore, the mechanical properties of Mg-Ag-Sn alloys at elevated temperatures.

Exploring the correlation between the density and the thermo-physical properties of the Al₂O₃-CaO-MgO-SiO₂ quaternary slag system is a subject of great interest in the domain of high alumina slag systems. This work attempts to establish correlations between (a) molar volume/density with enthalpy of mixing and (b) molar volume/density with slag viscosity, for the quaternary slag systems. The former is targeted based on existing models to determine the slag density and enthalpy of mixing first and then to develop machine-learning models which can suitably extrapolate the enthalpy of mixing as a function of slag composition, temperature and density. The volume shrinkage and the exothermic enthalpy of mixing between the slag constituent components are correlated in the current work. The later part would involve the conjunction of two hybrid machine-learning models, one for predicting slag viscosity as a function of slag compositions and temperature, and the other which predicts slag viscosity with the incorporation of slag density. The work will facilitate the establishment of two novel quantitative relationships that could provide better insights into the blast furnace quaternary slag systems.

Interactions of Ag and Sb(III) and Sn(IV) sulfides were investigated by x-ray diffraction, differential thermal analysis and microstructure analysis methods. The quaternary compound Ag₁₁Sb₃SnS₁₂ was found for the first time in the Ag₂S-Sb₂S₃-SnS₂ system at 500 K (227 °C) at the intersection of AgSbS₂-Ag₈SnS₆ and Ag₃SbS₃-Ag₂SnS₃. The compound melts congruently at 920 K (647 °C) and has a polymorphous transition at 646 K (373 °C). The quasi-ternary system is characterized by solid solution ranges of the binary compounds Ag₂S, Sb₂S₃, SnS₂, ternary Ag₃SbS₃, AgSbS₂, Ag₈SnS₆, Ag₂SnS₃ and quaternary compound Ag₁₁Sb₃SnS₁₂. The separation of the composition triangle into 10 single-phase, 18 two-phase, and 9 three-phase fields was established. Seven vertical sections were investigated of which five are quasi-binary (Ag₃SbS₃-Ag₈SnS₆, Ag₃SbS₃-Ag₂SnS₃, AgSbS₂-Ag₈SnS₆, AgSbS₂-Ag₂SnS₃, AgSbS₂-SnS₂). The AgSbS₂-Ag₄Sn₃S₈ and AgSbS₂-Sb₂SnS₅ sections are non-quasi-binary due to peritectic formation of Ag₄Sn₃S₈ and Sb₂SnS₅. The liquidus surface projection of the Ag₂S-Sb₂S₃-SnS₂ system consists of 10 fields of primary crystallization of the solid solutions α-Ag₂S, β-Sb₂S₃, γ-SnS₂, δ-Ag₃SbS₃, ε′-AgSbS₂, ζ-Ag₈SnS₆, η-Ag₂SnS₃, σ-Ag₁₁Sb₃SnS₁₂ and compounds Ag₄Sn₃S₈ and Sb₂SnS₅. These are separated by curves of monovariant equilibria that converge at 9 ternary invariant points (7 eutectic (E₁-E₇) and 2 quasi-peritectic (U₁, U₂)).

The thermodynamic optimization of the Gd-Cd binary system was carried out with the help of CALPHAD (CALculation of PHAse Diagram) method., GdCd₃, Gd₁₃Cd₅₈ and GdCd₈ have been treated as stoichiometric compounds while a solution model has been used for the description of the liquid, HCP_A3 (αGd), BCC_A2 (βGd) and HCP_A3 (Cd) phases. The intermetallic compounds GdCd,α-GdCd₂, β-GdCd₂, Gd₁₁Cd₄₅ and GdCd₆, which have homogeneity ranges, were treated by a two-sublattice model. The calculations based on the thermodynamic modeling are in a good agreement with the phase diagram data and experimental thermodynamic values.

The energy crisis and climate change have promoted a growing interest in non-fossil sources, such as nuclear, with uranium carbides being seen as potential fuel candidates for Generation IV nuclear reactors. However, the need of accurate thermophysical data for the fuel and its compatibility with core materials during the extreme fission conditions is still an issue. Here a study of the ternary uranium-iron-carbon system performed at 1100 °C using powder x-ray diffraction and Scanning Electron Microscopy coupled with Energy Dispersive Spectrometry is presented. The U-Fe-C isothermal section is characterized by two ternary compounds, thirteen 3-phase regions and five 2-phase regions. UFeC₂ and ~ U₁₁Fe₁₂C₁₈ were confirmed to be present at 1100 °C and crystallize in structures related to the binary uranium carbides. UFeC₂ crystallizes in an original structure type, a distorted variant of the UCoC₂ structure, with space group P4/n and a = 3.503(5) Å and c = 7.405(5) Å lattice parameters. ~ U₁₁Fe₁₂C_18, has a crystal structure related to the Th₁₁Ru₁₂C₁₈ structure-type (space group I (overline{4 }) 3m) with the lattice parameter a ≈ 10 Å. Furthermore, an island of a α-UC₂-based phase with 32U:4Fe:64C composition was found in the 1100 °C isothermal section, indicating the inclusion of Fe in the α-UC₂ binary compound.