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Bajenova I.,Thermochemistry of Materials Scientific Research Center | Fartushna I.,Thermochemistry of Materials Scientific Research Center | Khvan A.,Thermochemistry of Materials Scientific Research Center | Cheverikin V.,Thermochemistry of Materials Scientific Research Center | And 2 more authors.
Journal of Alloys and Compounds | Year: 2017

Phase equilibria upon crystallization in the Al-Mn-C system were studied using DTA, X-ray diffraction, SEM and electron probe microanalysis. The liquidus and solidus projections and the melting diagram (liquidus + solidus) for this system were constructed covering the whole concentration range. The ternary compound Mn3AlC (κ) (antiperovskite structure CaTiO3-type, ≿Р5-Pm-3m) melts congruently at 1320 °C. The liquidus surface consists of the binary compounds, the ternary compound Mn3AlC (κ) and solid solutions primary crystallization fields. The carbide Mn5C2 in the ternary system participates in equilibrium with the liquid phase in contrary to the binary system where it is formed from the solid state equilibrium. The solidus surface of the Al-Mn-C system in the region up to 50 at.% Al is defined by the co-existence of the κ-carbide with almost all phases of the binary subsystems: (С), (γMn), (εAlMn), (Al4C3), (Mn7C3) and (Mn5C2). The solidus surface in the region >45 at.% Al is defined by the co-existence of the carbide Al4C3 with all phases from Al-rich region. The DTA curves of the alloys with compositions close to the homogeneity region of phase (εAlMn), exhibit (on heating) an exothermic effect at ∼570 °C. This exothermic effect corresponds to the formation of the ordered metastable τ-phase, which is formed by mechanism: ε → ε’ (B19) → τ. τ-phase (AuCu, tP2-P4/mmm, a = 2.760, c = 3.600 Å) and which was observed in the alloys after heating up to 700 °C and slow cooling (5 °C/min). © 2016 Elsevier B.V.


Jacob A.,Jülich Research Center | Jacob A.,Vienna University of Technology | Schmetterer C.,Jülich Research Center | Khvan A.,Thermochemistry of Materials Scientific Research Center | And 3 more authors.
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2016

A liquidus projection and a thermodynamic assessment of the Cr-Fe-Nb ternary system are proposed for the first time. The construction of the liquidus projection was obtained through evaluation of the microstructure of as cast samples and high temperature DTA measurements of equilibrated samples. Thermodynamic modeling was then done via the Calphad method based on DFT calculation for the description of the energy behavior of the phases and experimental evidence. © 2016 Elsevier Ltd. All rights reserved.


Khvan A.V.,RWTH Aachen | Khvan A.V.,Thermochemistry of Materials Scientific Research Center | Hallstedt B.,RWTH Aachen | Broeckmann C.,RWTH Aachen
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2014

The availability of recent data on Gibbs energies of Fe7C 3 and Fe23C6 based on ab initio calculations required the complete reassessment of the thermodynamic parameters in the Fe-Cr-C system. In order to perform the optimization process a detailed critical evaluation of the experimental literature data on the Fe-Cr-C system was made. The Calphad technique using a computerized optimization procedure (PARROT) was applied in the work. Thus, a new self-consistent thermodynamic description of the Fe-Cr-C system based on a detailed literature survey was obtained in the present work. The results are presented in a number of phase diagrams. © 2014 Elsevier Ltd.All rights reserved.


Akhmetova A.M.,Thermochemistry of Materials Scientific Research Center | Dinsdale A.T.,Thermochemistry of Materials Scientific Research Center | Khvan A.V.,Thermochemistry of Materials Scientific Research Center | Cheverikin V.V.,Thermochemistry of Materials Scientific Research Center | And 2 more authors.
Journal of Alloys and Compounds | Year: 2015

Microstructural, XRD and DTA analysis of samples covering a range of compositions was carried out on cast and annealed samples in order to investigate phase equilibria in the Ag-Cu-Ge system. The results of the research work suggest the presence of a eutectic reaction L 虠(Ag) + ε + hcp instead of a quasi-peritectic reaction described by Dutkiewicz and Massalski. A larger extension of the (Ag) primary solidification region toward the Cu-Ge side of the phase diagram with Ge contents lower than 20 at.% and the extension of the ε phase primary solidification field toward (Ag) were observed in the present work. An EPMA analysis showed that there is limited solubility of Ag in the intermetallic phases of the Cu-Ge system. © 2015 Elsevier B.V. All rights reserved.


Khvan A.V.,Thermochemistry of Materials Scientific Research Center | Fartushna I.V.,Thermochemistry of Materials Scientific Research Center | Mardani M.,Thermochemistry of Materials Scientific Research Center | Dinsdale A.T.,Thermochemistry of Materials Scientific Research Center | Cheverikin V.V.,Thermochemistry of Materials Scientific Research Center
Journal of Alloys and Compounds | Year: 2015

The liquidus projection and invariant reactions involving the liquid phase in the Fe-Ce-C system were analyzed using microstructure investigation, X-ray diffraction (XRD) and differential thermal analysis (DTA). In contrast to a previous analysis of the phase diagram for the system three ternary eutectic reactions were observed. It was also observed that the region of primary solidification of the Ce2C3 phase has a deep extension towards Fe-C side of the system. © 2015 Elsevier B.V. All rights reserved.


Schmetterer C.,Jülich Research Center | Khvan A.,RWTH Aachen | Khvan A.,Thermochemistry of Materials Scientific Research Center | Jacob A.,Jülich Research Center | And 2 more authors.
Journal of Phase Equilibria and Diffusion | Year: 2014

A new thermodynamic assessment of the binary Cr-Nb system was performed using the CALPHAD method based on a review of the available literature and ab initio calculations for the hypothetical end members of the C15 Laves phase. Recent experiments reported in the literature revealed that there is no C14 type high temperature phase in this system, which is in contrast to most of the literature. A thorough analysis of these reports, however, showed that the C14 phase has never been directly observed and that its presence had been derived from ternary phase diagram data, twinning of the C15 low temperature phase and erroneous interpretations of x-ray diffractograms. Due to the lack of clear evidence in favor of its existence, the C14 phase was not considered a thermodynamically stable compound in the present evaluation. © 2014 ASM International.


Khvan A.V.,Thermochemistry of Materials Scientific Research Center | Dinsdale A.T.,Thermochemistry of Materials Scientific Research Center | Cheverikin V.V.,Thermochemistry of Materials Scientific Research Center | Kudashov D.,Engineering Technology Center | And 3 more authors.
Materials Science and Technology (United Kingdom) | Year: 2016

The influence of Mn and Cr on the formation of surface oxides and their entrapment during electric resistance welding of Si containing low carbon steels was studied using thermodynamic calculations and experimental investigation of the microstructure of the different oxide inclusions within welds on electric resistance welding-fabricated pipes. The process of oxidation during the welding process, its dependence on oxygen content, temperature of oxidation and the composition of ferrite within the parent steel were analysed. It was shown that the most important influence on the type of oxide inclusions formed during welding is the Mn/Si ratio, while Cr has an indirect influence via carbide formation, which increases the relative content of Mn in ferrite. © 2016 Institute of Materials, Minerals and Mining.


Syutkin E.A.,Thermochemistry of Materials Scientific Research Center | Jacob A.,Jülich Research Center | Schmetterer C.,Jülich Research Center | Schmetterer C.,Fraunhofer Institute for Environmental, Safety and Energy Technology | And 3 more authors.
Thermochimica Acta | Year: 2016

Standard enthalpies of formation, ΔfH, of the Laves-phases within their solid solutions along the Cr2Nb-Fe2Nb section were measured using drop solution calorimetry for the first time. The enthalpy values change linearly from -2.9 kJ mol-1 atom-1 for binary C15-Cr2Nb to -13.6 kJ mol-1 atom-1 for C14-Fe2Nb. The obtained values are compared with some earlier results on the binary compounds gathered mostly from ab initio calculations. © 2015 Elsevier B.V. All rights reserved.


Fartushna I.,Thermochemistry of Materials Scientific Research Center | Khvan A.,Thermochemistry of Materials Scientific Research Center | Dinsdale A.,Thermochemistry of Materials Scientific Research Center | Cheverikin V.,Thermochemistry of Materials Scientific Research Center | And 2 more authors.
Journal of Alloys and Compounds | Year: 2016

Phase equilibria in the Fe-Mn-Ce system were studied using DTA, X-ray diffraction, SEM and electron probe microanalysis. Liquidus and solidus projections for this system over the whole concentration range were constructed. The ternary compounds Fe11Mn6Ce21) (Th2Ni17-type) and Fe5Mn7Ce (τ2) (ThMn12-type) solidify incongruently by peritectic reaction L + (γFe,Mn) + (Fe2Ce) → τ1 and L + (γFe,Mn) + τ1 → τ2 at 974 and 953 °C, respectively. These ternary compounds are located along lines of constant Ce concentration of 10.5 and 8 at.% Ce, respectively, and have significant homogeneity ranges. The homogeneity range of the τ1-phase extends from 20 to 36 at.% Mn. The homogeneity range of the τ2-phase extends from 35 to 78 at.% Mn. The solubilities of Mn in Fe17Ce2 and Fe2Ce were established to be 18 and 33 at.%, respectively. © 2015 Elsevier B.V. All rights reserved.


Fartushna I.,Thermochemistry of Materials Scientific Research Center | Khvan A.,Thermochemistry of Materials Scientific Research Center | Dinsdale A.,Thermochemistry of Materials Scientific Research Center | Cheverikin V.,Thermochemistry of Materials Scientific Research Center | And 2 more authors.
Journal of Alloys and Compounds | Year: 2016

Phase equilibria in the Fe-Mn-Ce system at 900 °C were studied using DTA, X-ray diffraction, SEM and electron probe microanalysis. Using the results an isothermal section at 900 °C for this system was constructed covering the whole concentration range. The stability of the ternary compounds Fe11Mn6Ce2 (τ1) and Fe5Mn7Ce (τ2) at 900 °C, identified previously, was confirmed. The ternary compound τ1 is located along a line with a constant Ce concentration of 9.6 at.% and its homogeneity range extends from 20 up to 34 at.% Mn at 900 °C. The ternary compound τ2 is located along a line with a constant Ce concentration of 8 at.%. Its homogeneity range extends from 35 up to ∼70 at.% Mn at 900 °C. The phases βFe17Ce2 and Fe2Ce, both of which dissolve appreciable quantities of Mn, are located along lines with constant concentrations of Ce of 10.8 and 33 at.%, respectively. The solubilities of Mn in βFe17Ce2 and Fe2Ce were established to be 18 and ∼28 at.%, respectively. At 900 °C the liquid phase is stable in the Fe-Mn-Ce system. The isothermal section is characterized by eight three-phase regions: (αFe) + (γFe,Mn) + (βFe17Ce2), (γFe,Mn) + (Fe2Ce) + (βFe17Ce2), (γFe,Mn) + (Fe2Ce) + τ1, (γFe,Mn) + τ1 + τ2, τ1 + τ2 + (Fe2Ce), (γFe,Mn) + (βMn) + τ2, L + (βMn) + τ2 and L + τ2 + (Fe2Ce) plus the corresponding two-phase regions. © 2015 Elsevier B.V. All rights reserved.

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