The phase diagram of the Al–Cu–Zn ternary system was re-investigated experimentally. The current study was designed to contribute to a better description of those parts of the phase diagram, which ...are disputed in the current scientific literature. Mutual relations in the family of ternary intermetallic phases
τ
with cubic, rhombohedral and modulated structure at temperatures 400 °C and 550 °C were described. The phase relation between the
γ
and
γ
′ phases was studied at different temperatures. A two-phase field between
γ
and
γ
′ was observed below 400 °C, while the transition appears to be second order at higher temperatures. A vertical section between
γ
and
γ
′ phases in Cu–Zn and Al–Cu and four isothermal sections at 400 °C, 550 °C, 700 °C and 820 °C, respectively, were constructed.
The phase diagram of the Al–Cu–Si ternary system was investigated experimentally at the temperatures 600 °C and 800 °C. The current study was designed to contribute to a better understanding of the ...ternary phase diagram Al–Cu–Si at elevated temperatures, where some of the phase equilibria were only tentatively known. It was found that the ternary phase τ proposed earlier is actually an extended solid solution of Al in the CuSi_δ phase. At 700 °C, the phase CuSi_δ is stable as a pseudo ternary phase, and the existence of a significantly extended thermal stability range in the ternary was also confirmed by DSC measurements. In agreement with previous isothermal sections at other temperatures, a huge solubility of aluminum in CuSi_κ and negligible solubility of Si in AlCu_β was observed.
Three isothermal sections of the Ni-Se-Sn ternary system were experimentally investigated at 800 K, 1000 K and 1100 K in whole composition range. One stable ternary intermetallic phase, Ni
5.62
SnSe
...2
, was confirmed. Solubility up to 15 at.% of tin was observed in the binary phase NiSe. Metastable binary phase Ni
3
Se
4
was found at 800 K probably stabilized by third element. Complete isothermal sections at 800 K, 1000 K and 1100 K are proposed in this paper.
The ternary phase diagram Ag-Se-Sn was re-investigated experimentally. The current study was designed to contribute to a better understanding of phase equilibria in isothermal sections at 250, 400 ...and 550 °C using long-term annealed samples. An intermediate liquid region was observed at 550 °C in agreement with older published vertical sections of the ternary phase diagram Ag-Se-Sn. A huge homogeneity range in ternary intermetallic phase Ag
8
Se
6
Sn at 250 °C was determined by SEM/EDX analysis of long term annealed samples and confirmed by XRD measurements. A second ternary phase AgSe
2
Sn was observed at each of the studied temperatures. Complete isothermal sections at 250, 400 and 550 °C were constructed in the scope of this paper.
► Description of the Calphad method for the modelling of phase diagrams. ► Overview of conditions for the creation of a consistent thermodynamic database. ► Examples of the phase diagram modelling ...and its exploitation for practical use. ► Application of the Calphad method for other modelling in macro and micro-scale.
The Calphad method is very important method for the modelling of thermodynamic properties and phase diagrams of multicomponent systems. The method is based on a semi-empirical approach and sequential modelling from simpler to more complicated systems. Therefore reliable experimental data are necessary for the description of the thermodynamic and phase properties of unary and binary systems. Basic principles of the method will be described in this paper, especially from the point of view of preparing the reliable theoretical thermodynamic description of simpler systems, which allow reliable prediction and assessment of higher order systems.
The thermodynamic data, describing assessed binary and ternary systems are collected in the form of the thermodynamic databases, which allow (together with proper software) the prediction of properties for multicomponent systems corresponding to real materials. The software packages, based on Calphad method, are currently the only theoretical tools, applicable for complex materials as steels, superalloys, etc.
The thermodynamic databases and outputs of the theoretical calculations are also important for many other applications and multi-scale simulations. They serve as input for phase field simulations, diffusion processes modelling, phase transformations, material properties and structure morphology development, including the processes on interface.
CALPHAD-Type Assessment of the Pb-Se-Sn System Zobac, Ondrej; Zemanova, Adela; Chen, Sinn-Wen ...
Journal of phase equilibria and diffusion,
04/2022, Letnik:
43, Številka:
2
Journal Article
Recenzirano
CALPHAD-type theoretical assessment of the Pb-Se-Sn system was carried out. This assessment is part of a larger project aimed at developing an Ag-Pb-Se-Sn-Te thermodynamic database which should serve ...for the development of materials for thermoelectric applications. The experimental results from the literature were used but they are quite sparse and significant inconsistencies have been found between experimental data published by various authors, especially in the Se-rich regions. In general, a reasonable agreement was obtained for the theoretical and experimental sections of the phase diagram and for the enthalpies of mixing of the liquid phase in the region with low selenium content, but the agreement is rather qualitative in the Se-rich region.
The Al–Cu binary system has been investigated intensively in the past as key binary system for many important industrial alloys. With respect to new experimental results about phase equilibria in ...Al–Cu system, it was found necessary to prepare new CALPHAD-type thermodynamic description of the Al–Cu system. In course of this work, the known crystallography of several intermetallic phases and the information about site occupations in particular crystallographic positions were implemented in the new thermodynamic phase descriptions. The intermetallic phases were furthermore modelled with all their different temperature modifications. Very good agreement with the experimental results was reached both, for the Al–Cu phase diagram and for the calculated thermodynamic properties, namely the enthalpy of mixing, enthalpies of formation and thermodynamic activities.
The Ge-Ti binary phase diagram was remodeled using the
CALPHAD
approach implementing newly available experimental data and data from
ab-initio
calculations. The modelled phase diagram is based on a ...recently published experimental phase diagram, enthalpy of formation calculated by
ab-initio
methods, experimentally measured heat capacity of phases Ge
3
Ti
5
and Ge
5
Ti
6
, enthalpy of formation of Ge
3
Ti
5
at 298 K and enthalpy of mixing of liquid at 2000 K. A very good agreement with the experimental results was reached for Ge-Ti phase diagram and for the calculated thermodynamic properties, namely the enthalpy of mixing of the liquid phase at 2000 K and heat capacity of phases Ge
3
Ti
5
and Ge
5
Ti
6
.
The phase equilibria of the Al-Ge-Mg ternary phase diagram were experimentally studied at the temperatures of 250, 300, 400 and 450 °C. The ternary phase τ (Al
2
Ge
2
Mg) suggested by the earlier ...structural study was found to be stable at all temperatures studied. Detailed study of the phase equilibria containing the τ (Al
2
Ge
2
Mg) phase in the ternary system have been carried out. The average composition of this phase was found to be 36 at.% Al-36 at.% Ge–Mg. In contrast to the previously published binary Ge–Mg phase diagram, the solubility of Mg in Ge was found to be within a few atomic percent. It was also found that GeMg
2
intermetallic phase dissolves only small amount of Al but there is significant nonstoichiometricity with respect to the Ge/Mg ratio especially for lower annealing temperatures.
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