Journal of Phase Equilibria and Diffusion最新文献

Phase equilibria in the Pd rich region of the Au-Cu-In-Pd quaternary at 500 °C and 800 °C are investigated by SEM, EDX and XRD techniques. Part of the isothermal tetrahedron was constructed accounting for published data for bounding ternaries obtained earlier by the present authors. No quaternary phases were detected. The solubility of copper in the τ₁ phase of the Au-In-Pd ternary (AuCu₃ structural type) does not exceed 5 at.%. Gold solubility in the InPd₂Cu phase of the Cu-In-Pd ternary is not less than 18 at.% at 500 °C, and at least 15 at.% at 800 °C. Analytical description of the boundaries of the FCC solid solutions in the equilibrium with the InPd₃, InPd₂Cu and ternary τ₁ phase was performed for bounding Cu-In-Pd and Au-In-Pd ternaries as well as for the quaternary. The tie-lines of the equilibria, i.e. the compositions of the two phases in equilibrium, were described as a single entity. To this end, the approach used in the literature for regression analysis of phase compositions of the (γ + γ′) Ni based superalloys was modified. The parametric descriptions of the two-phase tie-lines’ centers and those of the distribution coefficients of the components between the phases were built. The choice of parametrization is discussed. In particular cases of the ternaries and quaternary studied using the content of one or two of the components as parameters proved to be quite satisfactory. Very good description of the solubility lines and solubility surface including rather fine details has been achieved.Please check and confirm the edit made in the article title.Ok

We have studied phase transformations in Cd_0.96Mn_0.04Te_0.98Se_0.02 solid solutions in the temperature range of 1080-1149 °C using differential thermal analysis (DTA). Following the "heating-dwell-cooling" procedure, we investigated the melt supercooling versus superheating, crystallization temperature versus dwell temperature, and crystallization rate versus crystallization temperature. We observed that the Cd_0.96Mn_0.04Te_0.98Se_0.02 alloy remained in a semi-liquid state over the dwell temperature range of 1089-1097 °C. Following a "heating-dwell-heating-cooling" procedure, we investigated the solid-phase volume fraction versus dwell temperature, melting temperature versus dwell temperature and melt crystallization rate versus dwell temperature. We observed that at dwell temperatures higher than 1097 °C, the solid phase completely disappeared in the sample, since the effect of melting was not observed, meaning that the sample was a single-phase melt. Despite the fact that the alloy was heated in every cycle up to 1147 ± 2 °C after the intermediate dwell, structural fragments formed during this intermediate dwell were still present even at higher temperatures and, as a result, affected the crystallization. The range of crystallization temperatures decreases with increasing intermediate dwell temperature. Such dependence can be interpreted as an alloy “memory” of its thermal history.

The Cu-Sn-P phase diagram is essential for understanding the metallurgical phenomena of Cu-Sn bronze, brazing filler metals, and Sn-Cu lead-free solder. In this study, the solidus, liquidus temperatures and solubilities of P in the Cu-rich of the Cu-P system were determined using the electron probe micro-analyzer and differential scanning calorimetry. In addition, the thermodynamic assessment of the Cu-Sn, Cu-P, Sn-P, and Cu-Sn-P systems was carried out based on the results of previous studies and experiments of the current study. An associate-solution model was employed for the liquid phase, and an order/disorder model was employed for the bcc-based phase. The calculated phase diagrams and thermodynamic properties were in good agreement with the experimental data. The parameter set reproduced the Cu-Sn-P ternary phase diagrams without introducing ternary parameters into the liquid phase. Thus, the proposed model can reproduce the full-range of the compositional phase diagram of the Cu-Sn-P system.

Here, a complete phase equilibria picture in the Cu-As-S system was obtained by experimental study of carefully crystallized via long-term thermal annealing alloys by means of methods of differential thermal analysis and powder x-ray diffraction, as well as using the available literature data. The projection of the liquidus surface, the isothermal section at 300 K, and some vertical sections of the phase diagram are presented and discussed. The fields of primary crystallization of phases, types, and coordinates of invariant and monovariant phase equilibria are determined. The presented phase diagram reflects four ternary compounds Cu₃AsS₄, Cu₁₂As₄S₁₃, Cu₆As₄S₉, and CuAsS, which are synthetic analogues of natural copper-arsenic sulfide minerals. Particular attention is paid to the Cu₂S-As₂S₃ section. It is shown that this section, in contrast to the literature data, is not quasi-binary. The thermodynamic data for copper-arsenic sulfides, previously obtained by the authors by the electromotive force method with Cu₄RbCl₃I₂ solid electrolyte, have also been revised. Experimental data on the partial thermodynamic functions of copper in some phase regions of the Cu-As-S system were processed taking into account the constructed new version of the solid-phase equilibria diagram and updated data on the standard thermodynamic functions of formation and standard entropies of the ternary compounds Cu₃AsS₄, Cu₁₂As₄S₁₃, Cu₆As₄S₉, and CuAsS were obtained.

The Mg-Sm phase diagram has been experimentally studied by x-ray diffraction, scanning electron microscope equipped with energy dispersive spectrometer, and differential scanning calorimetry. Five binary compounds, Mg₄₁Sm₅, Mg₅Sm, Mg₃Sm, Mg₂Sm and MgSm were confirmed to exist in the Mg-Sm system. In addition to Mg₂Sm and MgSm, Mg₃Sm was found to be a congruently melting phase. The Mg₅Sm and Mg₂Sm were found to be only stable at high temperatures and decompose above 400 °C in this work. A special effort was made to determine the extent of the solid solubility ranges of Mg₃Sm, Mg₂Sm, MgSm and, γ-Sm. The Mg-Sm binary system was modeled using the Calphad approach based on new experimental data of this work and all reliable experimental information from literature. A complete thermodynamic description of the Mg-Sm system is obtained and extensive comparisons between calculated and experimental data are presented, indicating that almost all available experimental and theoretical data are fitted satisfactorily.

Hydrides enable handling hydrogen at low pressure and near room temperature, offering higher volumetric densities than compressed or liquid hydrogen and enhancing safety. The CALPHAD method, rooted in the principles of thermodynamics, offers a systematic approach for predicting phase equilibria and thermodynamic properties in multicomponent materials. This comprehensive review paper aims to provide a detailed overview of the application of the CALPHAD method in the realm of metallic and complex hydrides. After an introduction to the fundamental thermodynamic aspects of hydrides, key elements of applying the CALPHAD method to model metal-hydrogen systems and complex hydrides are discussed. Subsequently, recent publications are reviewed, highlighting key findings and recent progresses in the field. Finally, the challenges that must be overcome to achieve further progress in this area are explored.

The phase diagram of the Fe-Zn binary system was evaluated based on the CALPHAD method with reference to the latest experimental data. The solubility ranges of the intermetallic compound phases, Γ-Fe₄Zn₉, Γ₁-Fe₁₁Zn₄₀, δ_1k-FeZn₇, δ_1p- Fe₁₃Zn₁₂₆, and ζ-FeZn₁₃ were modeled considering their structures consisting of Zn₁₂ icosahedra with Fe at the center (Fe₁Zn₁₂ clusters) as well as glue-like Fe and Zn atoms, and the miscibility gap between the δ_1k and δ_1p phases was also taken into account in the present calculations. The solubility of Fe in the liquid and (ηZn) phases that was confirmed as dozens of times larger than the values reported in the earlier literature could be calculated by introducing Fe₁Zn₁₂ associates to these solution phases. Consequently, all phase equilibria were adequately reproduced by the thermodynamic models and parameters revised in the present study.

Faceted morphology is common in the microstructures resulting from solid-state phase transformations in a wide range of crystalline materials. This study explains the faceted interfaces based on the concept of singular interfaces, which are characterized by key interfacial structures at two levels: the singular dislocation structure and the preferred state existing between the dislocations. It identifies interface geometries required by these structures at two stages: before and after dislocation generation. Methods to determine the interface geometries are reviewed. These methods enable quantitative interpretation of phase transformation crystallography features, including the interface orientations and the orientation relationship between the two phases, irrespective of whether these features are described as rational or irrational. The agreement achieved across different systems indicates the crucial role of geometric matching in the development of phase transformation crystallography. An example is provided for an illustration of the application of the two-stage approach, especially with an analysis in reciprocal space using a superimposed diffraction pattern.

The In-Sn binary alloy system exhibits several unusual features that challenge crystallographic and thermodynamic expectations. We combine first principles total energy calculation with simple thermodynamic modeling to address two key points. First, we evaluate energies along the Bain path to interpret the discontinuous transition between the phases α-In (Pearson type tI2) and β-In₃Sn (also Pearson type tI2) that are identical in symmetry. Second, we demonstrate that the solid solution phases β-In₃Sn and γ-InSn₄ (Pearson type hP1) exist at high temperatures only, and they exhibit eutectoid decompositions at low temperatures.

The creep properties of fully lamellar γ/α₂ titanium aluminides can be significantly improved by alloying with Nb, Ta or Zr. While the influence of these alloying elements on the γ-phase has already been examined, their diffusivity and strengthening properties in the α₂-phase are still lacking. In order to study the effect of Nb, Ta and Zr in α₂-Ti₃Al, the alloys Ti-33Al, Ti-33Al-5Nb, Ti-33Al-5Ta and Ti-33Al-5Zr were investigated using a diffusion couple approach and strain rate jump tests. The results show that Zr diffuses the fastest, followed by Nb and Ta. Furthermore, these alloying elements also increase the strength compared to a binary Ti-33Al alloy, from which Zr leads to the highest strength increase followed by Ta and Nb. The lower diffusivity of Ta becomes increasingly important at higher temperatures and lower strain rates resulting in a higher strengthening potential than Nb and Zr under such conditions.