Thermo-Calc Software Package Research Articles

On the influence of iron and silicon content on the phase composition of the Al-Fe-Si system

Increasing interest in intermetallic phases of the Al-Fe-Si system is associated with their high specific strength, corrosion and wear resistance, as well as the low cost of their production. To exhibit the most successful combination of properties, it is necessary to impart a specific compact morphology to the precipitated intermetallic phases. It is important to create an alloy with a composition capable of accepting plastic deformation. The purpose of the work is to develop the composition of an Al-Fe-Si system alloy capable of withstanding plastic deformation and determining the corresponding deformation interval. Based on computer modeling, an alloy composition capable of accepting plastic deformation was developed and the corresponding deformation interval was determined. The simulation was carried out in the ThermoCalc software package, TCAL8 database. It has been revealed that alloys with a high content of both silicon and iron are not characterized by the formation of a single-phase region, however, with a certain combination of alloy components, it is possible to achieve a quasi-single-phase structure, when the content of one phase is observed to be more than 90%. The solidus temperatures for different alloy compositions and the boundary conditions for the existence of phases have been determined. The α phase is present in the system from a temperature of 770°C up to a temperature of 446°C. In composition, it is found in the range from 5 to 35% iron with an amount of silicon of 10% and from 0 to 15% silicon with an iron content of 30%. The maximum amount of α phase was obtained for the Al60-65 alloy; Fe30-32; and Si5-10%, deformation temperature range is 600-450°C. Deformation in this region will ensure processing in a quasi-single-phase region without melting.

Influence of copper and silicon on phase transformations in the iron – carbon system

Influence of copper and silicon on phase transformations in the iron – carbon system

МОДЕЛИРОВАНИЕ ФИЗИЧЕСКИХ ПРОЦЕССОВ СОЗДАНИЯ МАТЕРИАЛОВ

Improving the mechanical properties of metals and alloys is at the heart of the efforts of materials scientists and metallurgists to ensure the reliability of modern structural materials under various conditions. The specificity of the material of the Al-Fe-Si system with a content of each component of more than 5% makes it impossible to obtain the material by traditional casting. Additive manufacturing of materials is a new promising direction, which, thanks to the thermal effect, effectively creates multicomponent systems with favorable properties. This work is devoted to the processes of modeling physical processes, in particular, obtaining a phase diagram of the state of the cermet material of the Al-Fe-Si system in the ThermoCalc software package. The relevance of the study is determined by the development of a technology for obtaining material with a given composition and properties by additive methods, the use of a flux minimizes the waste of charge elements and eliminates oxidation at high temperatures. At the same time, the high temperatures achieved during the implementation of the synthesis ensure the full formation of the required phase composition. The purpose of this study is to model a multicomponent Al-Fe-Si system with its further testing. The temperature conditions for the formation of phases in a material with a composition of 60–90 wt % aluminum, 0–30 wt % iron, with a constant silicon content of 10 % are considered. This composition is characterized by the formation of one ternary compound with a highly symmetrical type of crystal lattice - the α-AlFeSi phase, while this phase exists in the temperature range of 950°C - 400°C. The results obtained predict the susceptibility of the material to plastic deformation, but exclusively using heating to the temperature of the predominance of the α-AlFeSi phase. The results of the physical experiment are in good agreement with the obtained simulation results. After synthesis, the material has a characteristic cast microstructure. The data obtained make it possible to select the technological conditions necessary for further processing of the obtained material.

Investigation of the phase composition of the middlings with subsequent simulation of the compositions of potassium and sodium salts for the decomposition of arsenopyrite

The results of the study of tin-bearing middlings are presented. The mineralogical composition obtained by micro-X-ray diffraction analysis was determined and thermodynamic modeling, using the software package Thermo-Calc, was carried out. The aim of this work was a comprehensive study of the interaction of arsenopyrite and cassiterite with salts of alkali earth metals and the search for the optimum composition and ratio of salts for the decomposition of arsenopyrite into separate easily removable components. With the help of these results further work on the development of a complex technique for the selective separation of arsenopyrite and cassiterite and the extraction of tin and associated metals from these middlings is relevant.

Using explosion loading to obtain coatings of chromium carbide and titanium mixtures in deposition mode

The paper presents the results of studies into the microstructure, chemical and phase composition of coatings deposited on a steel substrate using the sliding explosive loading of Cr3C2 chromium carbide and titanium powder mixtures. The equilibrium phase composition of coatings was calculated by computational thermodynamic modeling using the Thermo-Calc software package. The structure and elemental composition were studied using a FEI Versa 3D scanning electron microscope with an integrated EDAX Apollo X system for energy dispersive X-ray microprobe analysis. A Bruker D8 Advance diffractometer was used for X-ray phase analysis. It was shown that when the powder layer is loaded by a sliding detonation wave, it can be shifted along the substrate surface due to the horizontal mass velocity component of compacted material particles. This shift causes the inner layer of the compacted powder and the surface layer of the substrate to melt as a result of friction. The presence of a liquid phase prevents the compacted powder layer deceleration so that the major part of it is removed from the substrate surface. The liquid phase remaining on the surface undergoes rapid quenching due to heat removal into the substrate and forms a deposited coating containing both the components of the initial powder mixture and the components of the substrate to be coated. It was established that the deposited layer structure features by extremely high dispersion (grain size does not exceed 250 nm), and its phase composition turns out to be close to a thermodynamically equilibrium one. When using powder mixtures of chromium carbide with 40% titanium, a coating is formed consisting of titanium carbide with a metal binder based on solid solutions of iron and titanium in chromium.

Precipitation Kinetics During Post-heat Treatment of an Additively Manufactured Ferritic Stainless Steel

The microstructure response of laser-powder bed fusion (L-PBF)-processed ferritic stainless steel (AISI 441) during post-heat treatments is studied in detail. Focus is on the precipitation kinetics of the Nb-rich phases: Laves (Fe2Nb) and the cubic carbo-nitride (NbC), as well as the grain structure evolution. The evolution of the precipitates is characterized using scanning and transmission electron microscopy (SEM and TEM) and the experimental results are used to calibrate precipitation kinetics simulations using the precipitation module (TC-PRISMA) within the Thermo-Calc Software package. The calculations reproduce the main trend for both the mean radii for the Laves phase and the NbC, and the amount of Laves phase, as a function of temperature. The calibrated model can be used to optimize the post-heat treatment of additively manufactured ferritic stainless steel components and offer a creator tool for process and structure linkages in an integrated computational materials engineering (ICME) framework for alloy and process development of additively manufactured ferritic steels.

THERMO-MECHANICAL ASSESSMENT OF HIGH ENTROPHY (Fe-Ni-Cx (X=0.3-0.5), (Fe-Cr-Cx (X=0.3-0.5) TERNARY ALLOYS SYSTEM USING CALPHAD METHOD

The thermodynamical assessment of high entropy alloys (Fe-Ni-Cx (X=0.3-0.5)), (Fe-Cr-Cx (X=0.3-0.5)) system is performed in this research work through FEDAMO database and Thermo-Calc software package. The high energy thermal analysis is manipulated for yield strength from FCC to BCC, precipitation from cementite to M7C3 (grain boundaries), Crack Susceptibility Coefficient for Fe-Ni-Cx ,Fe-Cr-Cx ternary alloys system at (1900-3000)K temperature with constant atmospheric pressure of 106 Pascal. The highest crack susceptibility coefficient for Fe-Cr-C, Fe-Ni-C system is found 2.21043, 0.26294 with mass percent of C 0.2500%, at 3000K of temperature with Mass percent. Yield strength from FCC to BCC is found 824.0453, 100.67063 for Fe-Cr-C, Fe-Ni-C ternary alloys. Phase transition is noted from cementite to M7C3 at 1346.77339 K. FCC_A1#3 phases with 0.98772 moles and 0.01228 mole Of M7C3 with 0 moles of M23C6 carbide phases observed. The comprehensive line investigation of mechanical properties is justified with simulation/computational inputs. The results are feasible for industrial sectors and metallurgical centers for operation. The alloy shows equilibrium and good stability.

Linkage of Macro- and Microscale Modeling Tools for Additive Manufacturing of Steels

Additive manufacturing (AM) offers several benefits including the capability to produce unique microstructures, geometrical freedom allowing for material and energy savings, and easy production lines with fewer post-processing steps. However, AM processes are complex and phenomena occurring at different length and time scales need to be understood and controlled to avoid challenges with, for example, defects, residual stresses, distortions, and alloy restrictions. To overcome some of these challenges and to have more control over the final product, computational tools for different length scales need to be combined. In this work, an 18Ni300 maraging steel part is studied to understand the link between the process parameters and the as-built microstructure. The temperature evolution during laser powder bed fusion is simulated using the MSC simulation software Simufact Additive. This result is then linked to microscale models within the Thermo-Calc software package to predict the elemental micro-segregation, martensite start (Ms) temperature, and martensite fraction. The different values of the key process parameters such as laser speed, laser power, heating efficiency, and baseplate temperature are considered, leading to different thermal histories. The thermal histories affect the elemental segregation across the solidification structure, which in turn results in different Ms temperatures at different locations of the built part. It is found that higher laser energy generally causes higher temperatures and higher cooling rates, which results in a larger degree of elemental segregation and lower Ms temperatures in segregated regions. Furthermore, the segregated regions are predicted to have Ms temperatures below 200°C, which would result in retained austenite when using a baseplate temperature of 200°C. On the other hand, by using a baseplate temperature of 100°C, all regions would reach temperatures below the Ms temperature, and an almost fully martensitic structure would be possible. In summary, it is demonstrated how the linkage of macro- and microscale modeling tools for AM can be used to optimize the process and produce the desired microstructure, thereby achieving the desired mechanical properties.

Структура и свойства промышленных полуфабрикатов из свариваемого коррозионностойкого алюминиевого сплава системы Al – Mg – Si – Cu

The results of comprehensive studies of a set of properties of experimental-industrial sheets and extruded profiles made of a new aluminum alloy V-1381 Al – Mg – Si – Cu systems (6xxxx series) are presented in the article. The alloy has shown high manufacturability in industrial production under extrusion, as well as in hot and cold rolling. Using the Thermo-Calc software package, the quenching mode of semi-finished products was selected, as well as the modes of artificial aging modes were investigated. It is shown that the alloy V-1381T1 is not inferior in its mechanical properties to the foreign analogue alloy AA6013, is characterized by a good combination of mechanical properties at room temperature (σu ≥ 380 MPa, σ0.2 ≥ 360 MPa, δ5 ≥ 13 %) and elevated temperatures, exceeds the widely used alloy D16chT in yield strength by 20%, while possessing a lower density, better corrosion resistance and ability to obtain welded joints. The new alloy V-1381 can be recommended for use in fuselage structural elements of aviation equipment, including replacing less corrosion-resistant non-welded alloys of the D16 type, which will increase the weight efficiency of the structure both due to increased strength and due to the replacement of riveted joints withwelded ones.

Influence of the Small Sc and Zr Additions on the As-Cast Microstructure of Al–Mg–Si Alloys with Excess Silicon

This research is devoted to the study effects of complex alloying of Al-0.3 wt. % Mg-1 wt. % Si and Al-0.5 wt. % Mg-1.3 wt. % Si alloys by small additions of Sc and Zr on the microstructure in the as-cast condition. The effect of small additions of these elements on the microhardness, electrical conductivity, grain size and phase composition of the indicated alloy systems was studied. The methods of optical and electron microscopy were used for the study. Moreover, the phase composition was calculated using the Thermo-Calc software package. The study showed a strong effect of the chemical composition of investigated alloys on the size of the grains, which, with a certain combination of additives, can decrease several times. Grain refinement occurs both due to supercooling and formation of primary Al3Sc particles in the liquid phase. Alloys based on Al-0.5 wt. % Mg-1.3 wt. % Si are more prone to the formation of this phase since a lower concentration of Sc is required for it to occur. In addition, more silicon interacts with other elements. At the same time, Al-0.3 wt. % Mg-1 wt. % Si requires lower temperature for complete dissolution of Mg2Si, which can contribute to more efficient heat treatment, which includes reducing the number of steps. TEM data show that during ingot cooling (AlSi)3ScZr dispersoid precipitates. This dispersoid could precipitate as coherent and semi-coherent particles with L12 structure as well as needle-shaped particles. The precipitation of coherent and semi-coherent particles during cooling of the ingot indicates that they can be obtained during subsequent multistage heat treatment. In addition, in the Al0.5Mg1.3Si0.3Sc alloy, metastable β″ (Mg5Si6) are precipitated.

Phase Transformations During Homogenization of Inconel 718 Alloy Fabricated by Suction Casting and Laser Powder Bed Fusion: A CALPHAD Case Study Evaluating Different Homogenization Models

Estimating the required homogenization time during post-heat treatment after alloy fabrication is critical for both casting and additive manufacturing (AM). In this work, three CALPHAD-based modeling approaches to estimate the homogenization time in order to dissolve the Laves_C14 phase into γ matrix are evaluated for Inconel 718 alloys made by suction casting and laser powder bed fusion. These values are compared with the homogenization at 1180 °C for different durations. The compositions of the γ matrix obtained from experiments are used as inputs for the first model. The first model involves single-phase diffusion simulations using the diffusion module (DICTRA) implemented in the Thermo-Calc software package with composition profile for the Laves_C14 phase either determined from experiments or calculated by the lever rule. The second model uses Scheil simulations for predicting the segregation profiles, which are used as inputs for single-phase simulations. In the third model, moving boundary simulations using DICTRA are performed using the composition of Laves_C14 phase from the lever rule. The homogenization time determined using the first model matches reasonably well with the experimental observation for the AM alloy. The second model is imprecise as the segregation from Scheil calculation is not reliable for AM alloy. The last model is inaccurate due to lack of mobility data for atomic diffusion in the Laves_C14 phase. The predicted homogenization times for the cast alloys using these models do not match with the experimental values. This necessitates the need for determining the mobilities for Laves_C14 phase for improving the accuracy of DICTRA simulations to estimate the homogenization time.

Experimental measurement of diffusion coefficients and assessment of diffusion mobilities in HCP Mg–Li–Al alloys

An atomic mobility database was established for the ternary HCP Mg–Li–Al system as a part of an ongoing effort to enable rapid development of novel lightweight Mg alloys. Three sets of three diffusion couples were assembled and annealed at temperatures ranging from 400 to 500 °C. Li concentration profiles were measured using a combination of Auger electron spectroscopy (AES) and inductively coupled plasma optical emission spectrometry (ICP-OES), while Al composition profiles were acquired using electron probe microanalysis (EPMA). The forward-simulation analysis (FSA) was employed to extract both interdiffusion and impurity diffusion coefficients from the collected experimental composition profiles. These measured diffusivity data were used to assess and iteratively optimize mobility parameters for the Mg–Li–Al system using the diffusion module within the Thermo-Calc Software package (DICTRA). The reliability of the assessed mobility parameters was further confirmed by two validation diffusion couples that were annealed at 425 and 475 °C for 96 and 48 h, respectively. It was observed that additions of Li increased the diffusivity of Al in HCP Mg, whereas additions of Al decreased the diffusivity of Li in HCP Mg.

Interdiffusion and atomic mobility in the bcc Ti–rich Ti–Cr–Mn system

In this work, ternary interdiffusivities in the bcc Ti–rich Ti–Cr–Mn alloys at 1273 K were determined by using the combination of the diffusion couple technique and the Matano–Kirkaldy method. Subsequently, on the basis of the presently obtained interdiffusivities along with the diffusivity and mobility parameters of binary sub–systems within the Ti–Cr–Mn system and thermodynamic descriptions for the bcc Ti–Cr–Mn system, the atomic mobilities of Ti, Cr and Mn in the bcc Ti–Cr–Mn alloys were assessed using the optimization module within the Thermo-Calc software package. Moreover, the comprehensive comparisons between the experimental diffusion properties (i.e., interdiffusivities, composition profiles, and diffusion paths) and the calculated/model–predicted data due to the present atomic mobilities were conducted in order to verify the reliability of the mobilities. At present, the atomic mobilities for the bcc Ti–Cr–Mn system can provide an accurate interdiffusivity matrix over a wide composition range.

Formulas for the Calculation of Temperatures and Concentrations of Carbon Responsible to the Parar Equilibrium of the Main Phases in Medium Sheet Steels

With the help of the Thermo-Calc software package, arrays of calculated data were created for carbon concentrations in ferrite and austenite, corresponding to the para-equilibrium of these phases and their para-equilibrium with cementite, as well as for the corresponding temperatures A1 and A3. Marked arrays were obtained in wide temperature ranges for ranges of carbon concentrations and the most important substitution alloying elements (Mn; Si; Cr; Ni; Mo), covering the respective ranges for medium carbon and moderately alloyed steels. Analytical formulas were developed on the basis of the reference data arrays for calculating para-equilibrium concentrations of carbon in ferrite and austenite (depending on temperature and chemical composition), as well as temperatures A1 and A3 (depending on chemical composition), which allow to reproduce with high accuracy the results obtained using Thermo-Calc.

Continuous Casting of High Carbon Steel: How Does Hard Cooling Influence Solidification, Micro - and Macro Segregation?

One technology that is often employed in continuous casting of high-carbon steel billets to minimize centre - (or macro) segregation is hard secondary cooling. Investigations unanimously show, that hard cooling significantly reduces macro-segregation, but a mechanism for the reduced segregation is rarely given. In this paper the solidification of high carbon tire cord grade C80D cast as a 150x150 mm billet is calculated using the proprietary SMS Group solidification simulation package CHILL using steel properties calculated with the Thermo-Calc Software package and TCFE steels database. The obtained cooling rates in the billet for hard and soft secondary cooling are used to run solidification simulations considering solute redistribution using the diffusion module DICTRA. It is shown that for cooling rates achieved in continuous casting the steel solidifies far away from equilibrium. The solidification profile and solidus temperature lie in between the Scheil solidification model and the para-equilibrium Scheil model with carbon defined as a fast diffusing element. The calculated cooling rates and temperature gradients are used to simulate the solidification microstructure 20 mm from the billet surface using the phase field approach and the MICRESS® software package linked to Thermo-Calc through the TQ interface. This model clearly shows, that the most probable mechanism by which hard cooling reduces segregation is trapping of solutes between the intricately branched dendrite microstructure that results from the steep temperature gradients achieved when applying hard secondary cooling.

Austenite grain growth of medium-carbon alloy steel with aluminum additions during heating process

In this study, the effects of heating temperature (850–1100°C) and holding time (30–150 min) on the grain growth behavior of austenite in medium-carbon alloy steel were investigated by conducting experiments. The abnormal grain growth and mixed grain structure phenomenon are explained using an equilibrium precipitation phase diagram calculated by Thermo-Calc software package. The AlN particles were observed by field-emission scanning electron microscopy (FESEM), and the amount of AlN precipitations was detected by electron probe microanalysis (EPMA). Based on the research results, it was found that the average grain size of austenite in the test steel increased continuously with the increase of temperature and holding time. Furthermore, the abnormal growth of austenite occurred in the test steel at 950°C, and the heating temperature affected the austenite grain size more significantly. In addition, the decline in the amount of AlN second-phase particle in the test steel, which weakened the “pinning” effect on austenite grain boundaries, resulted in abnormal growth and the development of mixed austenite grain structures. The prediction model for describing the austenite grain growth of medium-carbon alloy steel during heating was established by regression analysis of the experimental data, and the model was verified to be highly accurate.

Temperature range definition of phase transformation in experimental biocompatible Ti-Nb-Zr system alloys by various methods

Abstract The calculated dependences of the α- and β-phases volume fractions change in the 300–600 °C temperature range and thermodynamic equilibrium temperatures of polymorphic α + β-β-transformations (β-transus temperature, Tβ) for biocompatible alloys of the Ti-39%Nb-xZr system, where x ≈ 5; 7; 9 wt% were defined by thermodynamic calculations using ThermoCalc software package. It is established the zirconium in Ti-Nb-Zr system behaves as a β-stabilizer rather than a neutral element, and provides a Tβ decreasing with an increase of its content in the alloy. An equation is proposed for calculating Tβ in ternary alloys of the Ti-Nb-Zr system, where Ci – chemical element concentration, at.%: Tβ = 882.5 − 12.68CNb − 5.56CZr. The equation was obtained from the data on the change of Tβ in the equilibrium binary Ti-Nb, Ti-Zr systems. The Tβ values, calculated according to this equation, were close to those obtained by thermodynamic calculation (the difference does not exceed 4 °C). It was shown that the temperature of the endothermic peak minimum on the DSC heating curves of the Ti-Nb-Zr system alloys caused by the α + β-β-transformation corresponds to the Tβ determined using the ThermoCalc software. The endothermic peak intensity was found to decrease with an increase of the zirconium content, which additionally confirms the β-stabilizing effect of zirconium.

Kinetic Simulations of Diffusion-Controlled Phase Transformations in Cu-Based Alloys

In this chapter, we present computational kinetics of diffusion-controlled phase transformations in Cu-based alloys, which becomes possible only most recently due to the establishment of the first atomic mobility database (MOBCU) for copper alloys. This database consists of 29 elements including most common ones for industrial copper alloys. It contains descriptions for both the liquid and Fcc_A1 phases. The database was developed through a hybrid CALPHAD approach based on experiments, first-principles calculations, and empirical rules. We demonstrate that by coupling the created mobility database with the existing compatible thermodynamic database (TCCU), all kinds of diffusivities in both solid and liquid solution phases in Cu-based alloys can be readily calculated. Furthermore, we have applied the combination of MOBCU and TCCU to simulate diffusion-controlled phenomena, such as solidification, nucleation, growth, and coarsening of precipitates by using the kinetic modules (DICTRA and TC-PRISMA) in the Thermo-Calc software package. Many examples of simulations for different alloys are shown and compared with experimental observations. The remarkable agreements between calculation and experimental results suggest that the atomic mobilities for Cu-based alloys have been satisfactorily described. This newly developed mobility database is expected to be continuously improved and extended in future and will provide fundamental kinetic data for computer-aided design of copper base alloys.

Assessment of the Al-Bi-Mg system and extrapolation to the Al-Bi-Mg-Sn quaternary system

The phase equilibria in the Al-Bi-Mg-Sn quaternary system have been studied using the CALPHAD (CALculation of PHAse Diagram) method. One of the four ternary systems constituting the quarternary system, the Al-Bi-Mg system, is re-assessed by means of the CALPHAD technique and Thermo-Calc software package, in consideration of the associate model for the liquid phase instead of the Modified Quasi-chemical Model used in the literature report. While for the other three ternary systems, the Al-Bi-Sn, the Al-Mg-Sn and the Bi-Mg-Sn systems, the thermodynamic parameters are mainly adopted from the literature reported optimization results with a little modification to the Al-Bi-Sn and the Al-Mg-Sn systems for the compatibility of all the constituent binary systems. The assessment results of the Al-Bi-Mg ternary system are in good agreement with the available experimental phase relations, including the liquidus surface projection and the vertical sections. The thermodynamic database of the Al-Bi-Mg-Sn quaternary system was developed without the consideration of the quaternary interactions and the quaternary compounds. With this newly developed thermodynamic database, the phase equilibria and the solidification processes of the ternary and the quarternary systems are calculated and analyzed.

Thermodynamic modeling of the thulium–germanium binary system

The thulium–germanium binary system has been critically assessed by means of the CALculation of PHAse Diagram technique through Thermo-Calc software package. The thulium–germanium binary system contains nine phases based on eight compounds, the intermediate phases with no solubility ranges: Tm5Ge3, Tm5Ge4, Tm11Ge10, TmGe, Tm4Ge5, TmGe1.5, and Tm0.9Ge2 were treated as stoichiometric phases, while the compound with homogeneity range TmGe1.8 (TmGe1.8_LT and TmGe1.8_HT) was modeled using two sublattices model as (Ge,Tm)0.358(Ge)0.642. The liquid phase was modeled as substitutional solution phase, in which the excess Gibbs free energy was formulated with Redlich–Kister polynomial. The germanium (diamond_A4) and thulium (hcp_A3) were kept as pure element phases since no solubility of germanium in thulium and vice versa. The calculations based on the thermodynamic modeling agree well with the phase diagram data and few experimental thermodynamic values from the literature.