CALPHAD Method Research Articles

Influence of silicon on the structure and properties of high-strength cast aluminum alloy AZ5NF

The phase composition and the mechanical properties of the AZ5NF with various contents of silicon impurities alloy were investigated by both calculation and experimental methods. For evaluation of the alloy phase composition and the effect of the chemical composition, CALPHAD method integrated in Thermo-Calc software was applied. Further scanning electron microscopy technique a significant increase of the volume fraction of Mg2Si phase with an increase of silicon content from 0.1% to 0.3%. It is shown that in case of silicon content higher than 0,2 wt.% Mg2Si phase starts forming during equilibrium crystallization. This phase forms as the thin layers at the grain boundaries. This leads to brittle intergranular fracture and significant reduction of the alloy ductility both in the as-cast state and in T6 temper. Based on this limits for the silicon content in AZ5NF have been proven. It is shown that dissolution of Mg2Si phase (full or partial depending on silicon content) requires solid solution treatment. Following quenching and artificial ageing provide high strength and ductility.

Thermodynamic Optimization of the Ternary Ga-Sn-Te System Using Modified Quasichemical Model

Thermoelectric (TE) materials are of great interest to many researchers because they directly convert electric and thermal energy in a solid state. Various materials such as chalcogenides, clathrates, skutterudites, eutectic alloys, and intermetallic alloys have been explored for TE applications. The Ga-Sn-Te system exhibits promising potential as an alternative to the lead telluride (PbTe) based alloys, which are harmful to environments because of Pb toxicity. Therefore, in this study, thermodynamic optimization and critical evaluation of binary Ga-Sn, binary Sn-Te, and ternary Ga-Sn-Te systems have been carried out over the whole composition range from room temperature to above liquidus temperature using the CALPHAD method. It is observed that Sn-Te and Ga-Te liquids show the strong negative deviation from the ideal solution behavior. In contrast, the Ga-Sn liquid solution has a positive mixing enthalpy. These different thermodynamic properties of liquid solution were explicitly described using Modified Quasichemical Model (MQM) in the pair approximation. The asymmetry of ternary liquid solution in the Ga-Sn-Te system was considered by adopting the toop-like interpolation method based on the intrinsic property of each binary. The solid phase of SnTe was optimized using Compound Energy Formalism (CEF) to explain the high temperature homogeneity range, whereas solid solution, Body-Centered Tetragonal (BCT) was optimized using a regular solution model. Thermodynamic properties and phase diagram in the Ga-Sn-Te and its sub-systems were reproduced successfully by the optimized model parameters. Using the developed database, we also suggested several ternary eutectic compositions for designing TE alloy with improved properties.

Thermodynamic Assessment of the AF–CrF3 (A = Li, Na, K) and CrF2–CrF3 Systems

Understanding the corrosion mechanisms and the effect of corrosion products on the basic properties of the salt (e.g., melting point, heat capacity) is fundamental for the safety assessment and durability of molten salt reactor technology. This work focused on the thermodynamic assessment of the CrF2−CrF3 system and the binary systems of chromium trifluoride CrF3 with alkali fluorides (LiF, NaF, KF) using the CALPHAD (computer coupling of phase diagrams and thermochemistry) method. In this work, the modified quasi-chemical model in the quadruplet approximation was used to develop new thermodynamic modelling assessments of the binary solutions, which are highly relevant in assessing the corrosion process in molten salt reactors. The agreement between these assessments and the phase equilibrium data available in the literature is generally good. The excess properties (mixing enthalpies, entropies and Gibbs energies) calculated in this work are consistent with the expected behaviour of decreasing enthalpy and Gibbs energy of mixing with the increasing ionic radius of the alkali cations.

Corium Experimental Thermodynamics: A Review and Some Perspectives

More than 30 years ago a specialist meeting was held at Joint Research Center Ispra (Italy) from 15 to 17 January 1990 to review the current understanding of chemistry during severe accidents in light water reactors (LWR). Let us consider that, at the end of the 1980s, thermodynamics introduced in the severe accident codes was really poor. Only some equilibrium constants for a few simple reactions between stoichiometric compounds were used as well as some simple correlations giving estimates of solidus and liquidus temperatures. In the same time, the CALPHAD method was developed and was full of promise to approximate the thermodynamic properties of a complex thermochemical system by the way of a critical assessment of experimental data, a definition of a simple physical model and an optimisation procedure to define the values of the model parameters. It was evident that a nuclear thermodynamic database had to be developed with that new technique to obtain quite rapidly prominent progress in the knowledge of thermochemistry in the severe accident research area. Discussions focused on the important chemical phenomena that could occur across the wide range of conditions of a damaged nuclear plant. The most pressing need for improved chemical models is identified with condensed phase mixtures to model the corium progression. This paper reviews more than 30 years of experimental data production in the field of corium thermodynamics. This work has been conducted through multiple international programs (EURATOM, ISTC, OECD) as well as through more specific studies conducted at the national scale. This research has been capitalised in specific databases such as NUCLEA and TAF-ID, databases developed at IRSN and at CEA, respectively, and are now used in degradation models of the severe accident simulation codes. This research is presented in this paper. In the conclusion, we outline the research perspectives that need to be considered in order to address today’s and tomorrow’s issues.

Thermodynamic modelling of the ternary Bi-Ga-Te system for potential application in thermoelectric materials

Thermoelectric materials have drawn widespread attention because they can enable the direct conversion between electric and thermal energy. Over the years, different materials such as skutterudites, clathrates, intermetallic alloys, eutectic alloys, chalcogenides have been explored for Thermoelectric (TE) applications. Amongst the eutectic alloys, the Bi-Ga-Te system exhibits promising potential as a TE material. Accordingly, in this study, we performed the thermodynamic optimization and critical evaluation of binary Bi–Ga, Bi–Te, Ga–Te, and ternary Bi-Ga-Te systems using the CALPHAD method. It is observed that the Ga–Te system shows asymmetric liquid solution properties with strong negative enthalpy of mixing, whereas the Bi–Te liquid exhibits the symmetric regular solution behavior. Moreover, the Bi–Ga liquid solution has a positive enthalpy of mixing. Therefore, Modified Quasichemical Model (MQM) using pair approximation was utilized to describe the diversified thermodynamic properties of liquid solution in sub-binaries by taking into account the Short-Range Ordering (SRO). By merging the binary optimization results with a proper interpolation method, the liquid solution properties and phase diagram information in the Bi-Ga-Te ternary system were also reproduced successfully without any adjustable ternary parameter. Several ternary eutectic compositions were suggested for designing TE alloy with enhanced properties using the developed database.

Experimental measurement and thermodynamic evaluation of the Mg + Cu + Sr ternary system

Isothermal sections of the Mg + Cu + Sr ternary system at 300 and 400 °C were investigated using sixteen key samples. The equilibria relationship and phase composition of each sample were deterimined by scanning electron microscopy (SEM) equipped with an energy-dispersive spectroscope (EDS). A new phase (named Mg23-xCu77Srx) was found at the first time in the both isothermal sections. The crystal structure information within nineteen major diffraction peaks of the new phase Mg23-xCu77Srx were identified according to the present XRD results. Moreover, the solid solubility range of Sr in the compound Mg23-xCu77Srx was found to be 6.3 ≤ x ≤ 8.4 at. % with a constant value of about 77 at. % Cu. Six and seven three-phase equilibria regions in the Mg + Cu + Sr ternary system were determined at 300 °C and 400 °C, respectively. The maximum solid solubility of Mg in the terminal solution fcc was found to be 6.8 at. % at 300 °C and 6.4 at. % at 400 °C, respectively. The solid solubility limits of the compounds Mg38Sr9, Mg23Sr6 and Mg2Sr were determined to be 2.9 at. %, 2.7 at. % and 2.2 at. % at 300 °C, respectively. Furthermore, the solid solubility limits of the compounds Mg38Sr9, Mg23Sr6 and Mg2Sr were determined to be 3.0 at. %, 1.6 at. % and 2.8 at. % at 400 °C. The isopleths of the Mg + Cu + Sr ternary system were analyzed combined with DSC measurement and CALPHAD method. Thermodynamic modelling of the Cu + Sr binary system and Mg + Cu + Sr ternary system have been carried out by the CALPHAD technique. The liquid solution was described using the modified quasi-chemical model in the pair approximation (MQMPA). The compound energy formalism (CEF) model was used for the solid solution phases. Thermodynamic evaluation of the Mg + Cu + Sr ternary system was carried out for the first time using the present experimental data. The obtained thermodynamic database of Mg + Cu + Sr ternary system will provide a favourable support for the Mg-based biodegradable implant development.

Thermodynamic modeling of the Al–Nb–V system

In the present work, the Al–Nb–V ternary system was thermodynamically modeled using the compound energy formalism (CEF) within the framework of the CALPHAD method and supported by ab initio calculations, which we report here for the first time. The thermodynamic descriptions of the Al–Nb, Al–V and Nb–V binary systems were taken from literature. Since it is not clear which is the best Al–V assessment available in the literature, three sets of thermodynamic parameters with three different thermodynamic descriptions of the Al–V system are proposed. End-member energies of Nb3Al and Nb2Al were obtained from first-principles electronic-structure calculations following the density functional theory (DFT). The optimized ternary parameters were based on experimental isothermal sections and liquidus projections data. The three sets of thermodynamic parameters show good agreement with experimental data. The new assessments successfully describe the miscibility gap between NbAl3 and VAl3 close to the Al–Nb system, the V solubility in Nb3Al, the tie-triangles Nb2Al-NbAl3-BCC and NbAl3-BCC-V5Al8, and the tie-lines between Nb3Al and BCC. In this sense, our work provides self-consistent thermodynamic descriptions of the Al–Nb–V system which can be used for the development of thermodynamic databases of higher order systems for refractory high-entropy alloys (RHEAs).

Processing, microstructure and high temperature dry sliding wear of a Cr-Fe-Hf-Mn-Ti-Ta-V high-entropy alloy based composite

High-entropy materials are promising for high-temperature applications. In order to achieve high-temperature wear resistance, a novel high-entropy alloy based composite, (CrMnFeHf)7.14(TiTaV)23.81, was designed and consolidated by spark plasma sintering at 1320 °C following thermodynamic simulations using the CALPHAD method. The microstructure of the sintered composite revealed a Ti30V36Ta19Cr5Mn5Fe4Hf1 body-centered cubic (bcc) high-entropy alloy matrix with C14 Laves phase and carbide particles. The Laves phase and carbide particles of higher hardness were formed in situ during the sintering in a bcc matrix. The dry sliding wear behavior of the composite against Si3N4 ceramic counter ball (10 N, 30 min) from room temperature to 600 °C was investigated. The high-entropy alloy composite showed a superior resistance to wear against Si3N4 ceramic due to the presence of reinforcing C14 laves phase and carbide particles in the high-entropy alloy matrix. Furthermore, the wear rate reduced with increasing temperature. The dominating wear mechanisms of the high-entropy alloy composite were adhesive wear and abrasive wear at room temperature and 200 °C, oxidation wear and abrasive wear at 400 °C and oxidation wear and delamination wear at 600 °C. The formation of multiple oxides, presence of Laves and carbide phase contributed to the low volume loss of high-entropy alloy composite during wear tests at high temperatures.

Experimental mixing enthalpy and thermodynamic modelling of UCl3-KCl system

The molar enthalpies of mixing (ΔmixHm) in the liquid potassium chloride-uranium(III) chloride mixtures have been measured with a Calvet-type high temperature microcalorimeter over the entire composition range at 1113 K. All the melts are characterized by negative enthalpies of mixing with a minimum value of about −17.5 kJ·mol−1. The minimum of the enthalpy of mixing is shifted towards the potassium chloride-rich compositions and located in the vicinity of xUCl3 ~ 0.40. The obtained results are discussed in terms of complexes formation in the liquid mixtures under investigation.Experimental mixing enthalpy data were used together with existing literature data in re-examination of KCl-UCl3 phase diagram. Analysis of the literature data on KCl-UCl3 phase diagram has indicated that all of them are not correct because the existence of K3UCl6 compound was ignored in spite of experimental facts pointing its existence. Reinterpretation of all existing data by CALPHAD method showed that the system under investigation is characterized by existence of K2UCl5 and K3UCl6 congruently melting compounds, and three eutectics (KCl-K3UCl6, K3UCl6-K2UCl5 and K2UCl5-UCl3, respectively). K3UCl6 solid compound exists at relatively narrow temperature range from about 800 K to congruent melting at about 892 K.

Experimental investigation and thermodynamic description of the Fe–Mo–Zr system

The phase relations at 1273 K and liquidus surface projection of the Fe–Mo–Zr system were investigated by means of electron probe micro-analyzer (EPMA), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD) methods. The composition range of C14 Laves phase was determined at 1273 K. The maximum solubility of Mo in C15–Fe2Zr, Mo in Fe23Zr6, Fe in C15–Mo2Zr and Zr in μ phase is about 4.8, 0.6, 17.7 and 4.6 at.% at 1273 K, respectively. The isothermal section at 1273 K of the Fe–Mo–Zr system on the whole composition ranges was constructed using 30 annealed alloys. In the liquidus surface projection, the primary solidification phase regions of bcc(Fe), C15–Fe2Zr, C14, μ, R, σ, bcc(Zr), C15–Mo2Zr and bcc(Mo) were experimentally confirmed using 31 as-cast alloys. Based on the experimental data in literature and the present work, the Fe–Mo–Zr system was optimized using CALPHAD method, and a set of self-consistent reliable thermodynamic parameters was obtained.

Modification of Lu's (2005) high pressure model for improved high pressure/high temperature extrapolations. Part II: Modeling of osmium–platinum system at high pressure/high temperature

In Part I of this paper, we have described a modification brought to the model of Lu (X.-G. Lu et al., Comput. Coupling Phase Diagr. Thermochem. 29 (2005) 49–55) in order to avoid extrapolation problems at high pressure and temperature. We now extend this approach to the study of a binary system: Os–Pt. For this, a complete description (equation of state) of Os at high pressure/high temperature is provided including the liquid phase. The thermodynamic assessment of the system Os–Pt has been carried out at ambient pressure by the Calphad method. All this study has been supported by first principles, special quasi-random structure (including under high pressure) and phonon calculations. Finally, using the high pressure description of metastable structures (hcp Pt and fcc Os), we have been able to obtain by extrapolation a complete description of Os–Pt system up to 500 GPa. Recent experimental data for Os–Pt system obtained up to 50 GPa at various temperatures up to 2300 °C may us allow to validate our modeling approach.

Theoretical and Experimental Studies of LiBH4–LiBr Phase Diagram

Because substitutions of BH4– anion with Br– can stabilize the hexagonal structure of the LiBH4 at room temperature, leading to a high Li-ion conductivity, its thermodynamic stability has been investigated in this work. The binary LiBH4–LiBr system has been explored by means of X-ray diffraction and differential scanning calorimetry, combined with an assessment of thermodynamic properties. The monophasic zone of the hexagonal Li(BH4)1–x(Br)x solid solution has been defined equal to 0.30 ≤ x ≤ 0.55 at 30 °C. Solubility limits have been determined by in situ X-ray diffraction at various temperatures. For the formation of the h-Li(BH4)0.6(Br)0.4 solid solution, a value of the enthalpy of mixing (ΔHmix) has been determined experimentally equal to −1.0 ± 0.2 kJ/mol. In addition, the enthalpy of melting has been measured for various compositions. Lattice stabilities of LiBH4 and LiBr have been determined by ab initio calculations using CRYSTAL and VASP codes. Combining results of experiments and theoretical calculations, the LiBH4–LiBr phase diagram has been determined in all composition and temperature ranges by the CALPHAD method.

Thermodynamic and Structural Properties of CuCrO2 and CuCr2O4: Experimental Investigation and Phase Equilibria Modeling of the Cu–Cr–O System

This work considers the equilibria between the stable phases of the Cr–Cu–O ternary chemical system at atmospheric pressure and in a large temperature range that includes the high-temperature liquid phase. Based on a thorough evaluation of literature data, we performed complementary experimental investigations of solid-phase properties (especially the mixed oxides) by implementation of spark plasma sintering and microanalysis, high-temperature X-ray diffraction combined with Rietveld analysis, differential thermal analysis, and thermogravimetry. We show that neither the spinel CuCr2O4 nor the delafossite CuCrO2 phases exhibit significant cationic nonstoichiometry. We provide an assessment of the thermodynamic functions of the spinel up to 1200 K, taking into account the α/β phase transition. We propose, for the first time, a consistent thermodynamic description of the Cr–Cu–O system based on the Calphad method, allowing the computation of reactions and phase equilibria, including the high-temperature liquid phase described by the modified quasichemical model.

Effective Design of Cr-Co-Ni-Ta Eutectic Medium Entropy Alloys with High Compressive Properties Using Combined CALPHAD and Experimental Approaches

Alloy design of Cr-Co-Ni-Ta eutectic medium entropy alloys (EMEAs) was performed through a CALPHAD method coupled with experimental study, with the aim to attain high phase stability as well as excellent mechanical properties. Based on calculated pseudo-binary diagram, CrCoNiTax (x = 0.1, 0.3, 0.4, 0.5, 0.7) medium entropy alloys were investigated. Two phases, FCC solid solution and Laves phase, were identified in the alloys. With increasing Ta content, the volume fraction of hard and brittle Laves phase increased, microstructure changed from hypoeutectic (Ta0.1, Ta0.3) to eutectic (Ta0.4) and then to hypereutectic (Ta0.5, Ta0.7). The stability of phases was assessed by considering the thermodynamic parameter Ω and valence electron concentration (VEC). The eutectic phases become stable when 1.42 < Ω < 0.74 and 7.5 < VEC < 8.25. In addition, based on nanoindentation, the results indicated that solid solution strengthening in γ phase was significantly enhanced, eutectic phase in CrCoNiTa0.4 EMEA was found to process the highest microhardness and elastic modulus. Finally, the hardness of alloys was positively correlated with the content of Ta and the plastic strain of alloys obviously decreased, while the compression strength firstly increased and then decreased. CrCoNiTa0.4 was the most promising alloy with the highest compression strength (2502 MPa) and high plastic strain (20.6%).

Thermodynamic modelling of the Al–Co–Fe system

In the present work, the Al–Co–Fe ternary system is thermodynamically modelled using the Calphad method. Experimental data such as liquidus, tie lines, phase boundaries, magnetic transition and order–disorder data points are included and critically examined. The data that has a better quality has been chosen to optimize the system. An order–disorder model has been used to describe the bcc and B2 phases. Experimental bcc/B2 transition data points were carefully examined and inconsistent data points were weighted less. A four-stage optimization was employed to fit the magnetic and bcc/B2 transitions and phase boundaries. The thermodynamic models of Al5Fe2, Al5Co2, Al2Fe, and Al9Co2 are adjusted to include the third element to reflect the solubility of this element in the ternary system. Ternary interaction parameters for bcc and fcc were optimized, using all the relevant experimental data in the literature. The calculation of isothermal and vertical sections are performed using the optimized model parameters and compared with the experimental data. A comparison between modelling and experimental measurements showed a good agreement between the present results and experiments.

Thermodynamic calculation and solidification behavior of the La-Pr-Fe and Ce-Pr-Fe ternary systems

Phase equilibria and solidification behavior of the La-Pr-Fe and Ce-Pr-Fe ternary systems were carried out through experimental investigation and thermodynamic calculation. Phase transition temperatures and solidification microstructure of La-Pr-Fe and Ce-Pr-Fe ternary alloys were studied by means of differential thermal analysis (DTA) and scanning electron microscopy with energy dispersive spectra (SEM-EDS). Based on the experimental results determined in this work and reported in the literature, the La-Pr-Fe and Ce-Pr-Fe ternary systems were calculated by the CALPHAD method, and reasonable thermodynamic parameters of these two ternary systems were obtained in this work. The calculated isothermal section and vertical section of the La-Pr-Fe and Ce-Pr-Fe ternary systems are in good agreement with the experimental results. The solidification processes of as-cast La-Pr-Fe and Ce-Pr-Fe ternary alloys were analyzed through thermodynamic calculation with Scheil model, which is satisfactorily consistent with the experimental solidification microstructure.

Design, phase equilibria, and coarsening kinetics of a new [formula omitted] precipitation-hardened multi-principal element alloy

Multi-principal element alloys (MPEAs), with dispersed nanometric precipitates in a ductile matrix, are attracting a considerable amount of literature’s attention. Understanding the coarsening kinetics and potential properties of such alloys is crucial for future developments in the field. In the present study, we report a new precipitation-hardened multi-principal element alloy, Cr29.7Co29.7Ni35.4Al4.0Ti1.2 (at%), developed with the aid of the CALPHAD method. The alloy has a tough Cr-Co-Ni FCC matrix and nanometric L12 precipitates. After standard heat treatments, the alloy was aged at 850 °C for different aging times and the coarsening kinetics was investigated. The evolution of mechanical properties as a function of aging time was evaluated through microhardness tests. An increment of 106 HV 0.5 was observed compared to the sample in the solution-treated condition. This hardness increment was higher than that of conventional superalloys with a similar volume fraction of precipitates. Experimental data indicate that particle growth during coarsening is governed by diffusion controlling mechanism. The coarsening rate constant was lower than that of traditional wrought superalloys aged at the same temperature, indicating better thermal stability of the current MPEA. Furthermore, experimental particle size distributions show a good correlation with the curve predicted by the Lifshitz–Slyozov–Wagner (LSW) theory. Deviations and the applicability of this theory for MPEAs are discussed.

Novel high entropy alloys as binder in cermets: From design to sintering

In recent years a new group of alloys has emerged breaking with the classical alloying concepts of physical metallurgy, high entropy alloys (HEA). Their main characteristic is that these alloys present 4 or 5 main elements increasing the entropy of the system and favouring the formation of a single phase. The disordered solid solution leads to develop an alloy with improved properties, in particular high thermal stability, hardness and strength. These properties make this group of alloys attractive as potential candidates for alternative binders in hard materials. In this work, two new compositions have been designed with the aim of obtaining a single BCC phase, reducing the cost and minimizing the presence of critical elements using elements that can present good potential properties for a cermet and with low toxicity and price such as Al, Cr, Mo, Ni, Fe and Ti. The design has been made based on the composition calculation applying the HEA phase formation empirical rules from literature in combination with thermodynamic simulations by Calphad method. The viability of the compositions has been studied through the processing of the compositions by casting and the study of wettability and solubility at high temperature on the hard phase of TiCN. Once the chosen compositions have been validated as competitive binders, cermets have been consolidated by spark plasma sintering (SPS) and the influence of the compositions on the mechanical properties of the compound materials has been studied.

Influence of Cu content on the microstructure and high-temperature tensile and fatigue properties of secondary AlSi7Mg0.3VZr alloys

The effect of Cu content on the microstructure and high-temperature tensile and fatigue behaviours of heat-treated secondary AlSi7Mg0.3VZr alloys were evaluated. Thermodynamic calculations based on the CALPHAD method were carried out to evaluate the formation of different phases. Tensile and fatigue tests were performed at room temperature and high temperature (300 °C) on alloys that were solution treated at 485 °C for 24 h and artificially aged at 180 °C for 8 h. The results show that the addition of Cu significantly improved the room temperature tensile properties at the expense of ductility, thus decreasing the fatigue behaviour at lower stress amplitudes. At 300 °C, Cu-bearing precipitates were responsible for the AlSi7Cu3Mg0.3VZr alloy having a better thermal stability than the AlSi7Mg0.3VZr alloy, leading to higher tensile and fatigue properties. After increasing the testing temperature, the effect of casting defects on fatigue crack propagation decreased, thus reducing the scattering of data independently of the Cu content. The fatigue failure mode changed from brittle to ductile at 300 °C for both alloys.

Predicting the composition of primary carbides of the multicomponent system Ni-5Cr-9Co-6Al-8.3W-4Re-4Ta-1Mo-1.5Nb-0.15C

Abstract. Problem. Development of new and optimization of existing casting alloys for the manufacture of blades of gas turbine engines for various purposes is an important scientific and technical problem. Given the sensitivity of the structural components to the concentration of alloying elements, there are difficulties in assessing the expected set of properties of the blades from the optimization of the chemical composition or structural state of alloys. Goal. The aim of this work is to study the specifics of the influence of alloying elements on the distribution of primary carbides in the structure, their topology, morphology and their composition for a multicomponent system such as Ni-5Cr-9Co-6Al-8,3W-4Re-4Ta -1Mo-1 , 5Nb-0.15C using the calculation method of CALPHAD prediction (passive experiment) in comparison with the data obtained by electron microscopy (active experiment). Methodology. Modeling of thermodynamic processes occurring during crystallization (cooling) or heating in the structure of alloys was carried out by the CALPHAD method. Results. The results of thermodynamic calculations of the chemical composition of carbides are presented in comparison with experimental data obtained by electron microscopy on a microscope REM-106I with a system of energy-dispersion X-ray spectral microanalysis. Originality. It is shown that when the total concentration of carbide-forming elements increases, the chemical composition of carbides also becomes more complicated. At a concentration of more than 2% of the mass. But in the alloy, in the carbide of MS, the content of tantalum prevails over the content of niobium, it also leads to a decrease in the concentration of tungsten and molybdenum in the carbide. It was found that when the concentration of niobium is more than 3 wt%. in the alloy, its content in the primary carbide exceeds the content of tantalum and the carbide becomes based on Ta. Practical value. On the basis of an integrated approach, computational and experimental, for multicomponent heat-resistant alloys, new regression models are obtained that allow to adequately predict the chemical composition of carbides by the chemical composition of the alloy. which is confirmed by the obtained experimental data.