Journal of Phase Equilibria and Diffusion最新文献

This study investigates the heat capacities of intermetallic phases, specifically Ni₃Fe, Ni₃Mn, Ni₃Ti, NiMn and TiAl, using differential scanning calorimetry (DSC), and enthalpy increments of Ni₃Ti, NiMn and TiAl by means of drop calorimetry. The experimentally derived heat capacities of the respective phases are described using an Extended-Einstein model (EE-model). The experimental data, the fitted heat capacities, and literature data are in good agreement. The study also assesses the reliability of the heat capacities using enthalpy increments measured between 680 and 890 K. Experimental heat capacity data for ordered binary intermetallic phases are crucial thermophysical properties for constructing multicomponent thermodynamic databases which support computational materials design.

The solidified microstructure and the corresponding surface corrosion resistance of the Zn-Al-Mg coated product were experimentally investigated, and the effects of cooling rate and alloy composition on the coated products were fully analyzed by means of CALPHAD (CALculation of PHAse Diagrams) calculations. Scanning electron microscopy, electron probe micro-analyzer, X-ray diffraction and glow discharge spectrometer methods were applied to study the micro-morphologies, phase compositions, phase structures and elemental distribution of Zn-Al-Mg alloy coatings resulting from different cooling rates, respectively. The Tafel polarization test and electrochemical impedance spectroscopy test were carried out to investigate the electrochemical feature of Zn-Al-Mg alloy coatings. It was found that the enrichment of Mg on the surface of the Zn-Al-Mg coating impairs its surface qualities. With the assistance of thermodynamic and kinetic simulations, it is suggested that both the cooling rate and the solidification sequence led to the enrichment of Mg on the coating surface. Alloy coatings including MgZn₂ phase at faster cooling rates have higher Mg enrichment on the coating surface. Therefore, it is necessary to have the phase transition MgZn₂↔Mg₂Zn₁₁ occur in the final solidification stage, reducing the Mg enrichment on the coating surface. The redesign of the alloy composition is aimed at changing the solidification sequence of the Al-rich Fcc_A1 phase and Mg-rich Mg-Zn compound and adjusting the ratio of the eutectic and primary phases, which can further improve the coating qualities of the industrial Zn-Al-Mg coated products.

In this work, we present a thermodynamic assessment of the praseodymium–thallium (Pr–Tl) binary system using the CALPHAD method, supported by ab initio calculations based on density functional theory (DFT) via the WIEN2k code. Due to the limited availability of experimental thermodynamic data for this system, six intermetallic compounds Pr₃Tl, Pr₂Tl, Pr₅Tl₃, PrTl, Pr₃Tl₅, and PrTl₃, were analyzed using a combined computational approach.

Their crystallographic structures were verified through comparison between DFT calculations and existing literature. Sublattice models and Gibbs energy formulations incorporating excess terms were employed to represent the compounds, five of which exhibit homogeneity ranges. The developed thermodynamic model successfully reproduces phase boundaries, solubility limits, and formation enthalpies in good agreement with both experimental observations and ab initio predictions. This integrated approach offers a consistent and reliable thermodynamic description of the Pr–Tl system and serves as a useful framework for future studies on rare-earth–thallium-based materials.

In this Supplemental Literature Review, the number of intermediate phases reported in the V–Zn phase diagram, which has increased from 2 to 4 over the years, has been discussed briefly. Next, in the Nb–Zn system, the viewpoints on most Nb–rich (Nb₃Zn, NbZn, or Nb₆Zn₇) and most Zn–rich (NbZn₁₅ or NbZn₁₆) phases have been discussed.

The solid-liquid phase equilibria in the Na₂O-Al₂O₃-SiO₂ system, relevant in several industrial applications, were experimentally investigated. The liquidus compositions in the ternary system, at temperatures ranging from 1200 to 1600 °C, at the saturation of solid SiO₂, Al₂O₃, and 3Al₂O₃·2SiO₂, were measured by the equilibration-quenching method using Energy-Dispersive x-ray Spectroscopy (EDS) and Electron Probe Microanalyzer (EPMA) technique. This study introduces a new approach to achieving equilibrium more quickly, which is often challenging due to the slow formation of 3Al₂O₃·2SiO₂ (mullite). Furthermore, the use of EDS and EPMA enhances the accuracy of the results, marking a significant improvement over previous studies that relied on petrographic analysis. The experimental data obtained were compared with findings from earlier studies and with computed phase diagrams derived from two well-established thermodynamic databases. The insights gained from this investigation contribute to the existing body of knowledge and the thermodynamic models related to the Na₂O-Al₂O₃-SiO₂ system.

The Ga-Nd binary system has been modeled using existing experimental data on phase equilibria and thermodynamic properties through the CALPHAD methodology. The Ga–Nd binary system contains six intermetallic compounds: (text{Ga}_{6}text{Nd}_text{rt}), ({text{G}text{a}}_{6}text{N}text{d}_text{h}text{t}), (:{text{G}text{a}}_{2}text{N}text{d}), (:text{G}text{a}text{N}text{d}), (:{text{G}text{a}}_{3}{text{N}text{d}}_{5}) and (:{text{G}text{a}text{N}text{d}}_{3}). All these compounds were modeled as stoichiometric phases, except for the (text{Ga}_2text{Nd}) compound, which exhibits a homogeneity range. It was described using a two-sublattice model with substitution on one sublattice. In addition to the intermetallic compounds, this phase diagram also comprises a Ga-rich solid solution, two Nd-rich terminal solid solutions ((text{Nd}_text{r}text{t}) and (text{Nd}_text{h}text{t})), and a liquid phase. The Gibbs energy of the liquid phase in the Ga–Nd binary system was modeled using the Redlich–Kister polynomial formalism, which describes deviations from ideal mixing. The temperature dependence of the interaction parameters was treated either as a linear function or using the exponential formulation proposed by Kaptay. The results obtained from the thermodynamic modeling show strong consistency with both the phase diagram data and the experimentally determined thermodynamic values reported in the literature. The thermodynamic parameters of the Ga–Nd binary system have been assessed for the first time, enabling the calculation of phase equilibria and thermodynamic properties for both the liquid phase and the intermetallic compounds.

Nowadays first-principles calculations have achieved considerable reliability for the prediction of the properties of materials. These calculations are based on the density functional theory. In the present work, we have obtained a large number of enthalpies of formation of binary intermetallic compounds of rare-earth metals (Sc, Y, and lanthanides) with Al, Ga, In, and Tl elements. This work was initiated with a study of binary rare-earth-boron systems. The ab initio values have been calculated with the Vienna ab initio simulation package in the generalized gradient approximation. We have compared the calculated enthalpies of formation of compounds to the values obtained with calorimetric methods. Good agreement is observed in the cases of aluminium and gallium based compounds. A less good agreement is observed with the In, and Tl based compounds. In the case of the In and Tl based compounds, we always observe that the experimental values are more negative than the calculated ones. All the results show similar behaviour of Sc and Lu on one hand and of Y and Gd on the other hand with the p subshell elements. The evolution of the enthalpies of formation along the rare-earth series has been discussed. The behaviour of a given rare-earth element with p elements belonging to a same column has also been discussed.

This study investigates the reaction between silicon carbide (SiC) and boron (B) at high temperature. A B/SiC diffusion couple treated at 1973 K (1700 °C) for 8 h under uniaxial pressure was analyzed using energy dispersive spectroscopy and electron probe microanalysis with wavelength dispersive spectroscopy. Distinct reaction zones were identified, and the reaction sequence was established as SiC/(B_xC)/SiB₆/(SiB_n)/(β-B). This sequence aligns with B-C-Si phase equilibria and driving force calculations, which predict (B_xC) as the first phase formed between B and SiC. The formation of ternary solid solutions is also discussed, comparing reported Si solubility in (B_xC) and B solubility in SiC with our findings. The boron carbide layer exhibits a composition gradient (13.7 at% C to 12.4 at% C) and was identified as a ternary solution with an average silicon content of 2.0 at%. This study is based on an unprecedented approach to interface reactivity in the B-C-Si system, relying on the experimental study of the B-SiC diffusion couple and thermodynamic calculations of phase equilibria. The results also highlight the relevance of the existing thermodynamic database for predicting phase equilibria in this system. However, the composition range of (B_xC) and (SiB_n) may require further investigation.

The fcc-based (Zr, Nb)₂Fe phase was previously recognized as a stable compound in the Zr–Nb–Fe system. Our study shows that (Zr, Nb)₂Fe is an O-stabilized phase (Zr, Nb)₄Fe₂O. The results indicate that the (Zr, Nb)₄Fe₂O is based on the ternary Zr₄Fe₂O_x phase in the Zr–Fe–O system.This study has identified four four-phase equilibria consisting of [βZr + Zr(Nb, Fe)₂ + (Zr, Nb)₄Fe₂O + liquid], [βZr + Zr(Nb, Fe)₂ + αZr + (Zr, Nb)₄Fe₂O], [ZrFe₂ + Zr(Nb, Fe)₂ + (Zr, Nb)₄Fe₂O + liquid] and [αZr + Zr(Nb, Fe)₂ + (Zr, Nb)₄Fe₂O + ZrO₂] in the Zr–Nb–Fe(O) alloys at 1000 ℃. Based on the current experimental findings, the phase relationships of the Zr–Nb–Fe(O) system at 1000 ℃ close to the Zr–Fe side were established.