Thermo-Calc Software Research Articles

Microstructure and Super-Elasticity of Fe-33Mn-17Al-8.5Ni (at. %) Alloy for Structural Applications

The control of the residually stressed γ’-FCC phase in the grain boundaries that affects super-elasticity in the promising Fe-Mn-Al-Ni shape memory alloy (SMA) and grain size enhancement was an epitome for research in the current study. New composition Fe-33Mn-17Al-8.5Ni (at. %) was designed with the help of thermocalc software TCFE 11 database, produced in an electric arc furnace under an argon atmosphere and systematically investigated in the as-cast and heat-treated conditions. Characterization was performed using optical microscopy, X-ray diffraction measurements (XRD), and compression tests. Controlling the cooling conditions after heat treatment (HT) with high flowrate air cooling helped to reduce on the formation of the detrimental phase, γ’ at the grain boundaries as well as observed some grain growth in the microstructure without necessarily causing cracking as reported previously with quenching in cold water. The yield strength depicting the stress-induced martensitic transformation was 925 MPa for as cast and 909 MPa upon heat treatment. From cyclic compression loading/deloading training, a recovery strain of 2.1% and 2.3% was attained at 800 MPa maximum stress in the as-cast and heat treated-conditions, respectively.

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

Morphology and Distribution of Primary Carbides in Forged Cr-Ni-Mo-V/Nb Steel.

This study aims to investigate in situ the three-dimensional (3D) morphology and distribution of primary carbides (PCs) in electro-slag remelting (ESR) forged 30Cr3Ni3Mo2V steel. A facile non-aqueous electrolytic etching method was applied to prepare 3D PCs on the matrix. The morphology, composition, and element concentrations of PCs were characterized using a combination of optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and electron back-scattered diffusion (EBSD). The precipitation, type, and composition of PCs in the same steel were also simulated using Thermo-Calc software Version 2015a. The results indicate that PC is rich in Nb, which is a potential heterogeneous nucleating agent. Both the size and number of PCs increase from the edge to the center of the ingot. The large-sized PCs present three dominant types of morphology, which vary in different regions, i.e., a bulky type dominates in the edge region, a lamellar type dominates in the middle region, and a stripy type dominates in the core region. The results of EBSD analysis show that the orientation of PCs with different morphologies is different and that more nanosized V-rich type carbides are precipitated on the matrix. The thermodynamic calculations show that MC precipitates from the liquid phase when the solid phase fraction is greater than 0.985 and that the MC-type carbides are rich in Nb, which agrees well with the experimental results.

Thermodynamic Modeling of Solid Flux Interactions with Molten Aluminum

Oxide and dross formation during aluminum melt processing results in a considerable amount of loss of metallic aluminum. The total melt loss generated during melt processing can be greatly reduced by efficient use of flux, particularly for melting aluminum scrap or secondary alloys. Effective use of cover fluxes can significantly reduce dross generation by creating a barrier between the metallic aluminum and the atmosphere. The amount of metallic aluminum trapped within the dross layer can also be reduced by up to 50% using drossing fluxes. However, reducing the industrial average melt loss has remained difficult. To evaluate flux ingredients used in the casting industry, computational thermodynamic software ThermoCalc was used to calculate the driving force for reactions between twenty-one flux ingredients and eighteen common alloying and impurity elements in foundry alloys. The thermodynamic calculations, combined with other properties, were used to provide a desirable list of cover and drossing ingredients, which are being experimentally validated.

Development and directed energy deposition of high strength Hf5Mo15Nb35Ta25Ti20 refractory high entropy alloys

In this study, a novel HfMoNbTaTi refractory high entropy alloy was designed by empirical calculations and CALculation of PHAse Diagram (CALPHAD) method by using ThermoCalc software. Directed energy deposition (DED) based additive manufacturing process was used to produce the alloy. After the process parameter determination studies using single-track productions, cuboids were produced. The microstructural investigations showed that while the central region of cuboids has large grains, the outer region has a dendritic structure with some unmolten Mo powders. Although columnar grain formation, which is the general characteristic of directional solidification, was observed at some points, irregularly shaped grains were dominant in the structure. Moreover, there were micron to nano-sized Hf-Ti-O particles inside the grains and especially around the grain boundaries. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirmed the formation of disordered body-centered cubic (BCC) Hf5Mo15Nb35Ta25Ti20 alloy with ∼6 vol% of Hf-Ti-O particles. Electron backscatter diffraction (EBSD) analyses indicated that there is a slight texture in the building direction along 〈111〉. In order to determine the stability of these alloys, ex-situ heat treatments coupled with XRD studies were conducted. As opposed to CALPHAD calculations it was not observed any HCP phase formation. Compression test results showed that Hf5Mo15Nb35Ta25Ti20 alloys have high strength (σy = ∼1300 MPa) and high compressive ductility with good strain-hardening ability. Theoretical calculations revealed that the strength of the alloy mainly originated from solid solution strengthening.

Production and Characterization of an Economical 1100 MPa Advanced High-Strength Silicon-Containing Steel

AbstractIn this investigation, an attempt has been made to identify the metallurgical properties with the change of silicon contents, either theoretically by utilizing Thermo-Calc (the Scheil–Gulliver model implemented in the Thermo-Calc software) or JMatPro software, as a computational prediction technique, in addition to experimental examinations by dilatometer. Microstructures of investigated steels were evaluated optically at low magnification using optical microscopy. Scanning electron microscopy was used to study the observed microstructure at high magnification. ASTM standard specification E-8 was utilized for measuring the tensile property values, while fracture surfaces of the tensile samples were inspected by EDS (point-analyzer) employed in scanning electron microscopy. The investigated steel’s as-polished surface was studied using the experimental results, which revealed that the steel microstructure ranged from full-bainitic to full-pearlitic structures according to the variation of silicon contents. The count of non-metallic inclusions decreased and vice versa by the area occupied by non-metallic inclusions with the rising silicon content. The steel containing silicon of 0.87 wt.% has the best toughness combined with high tensile strength and hardness incomparable with conventional steel. Elongation (16.2%) combined with an ultimate tensile strength (1113 MPa) was achieved for the steel containing 0.87 wt.% Si.

Influence of Cooling Rate and Alloying by “Cr, V, and Ni” on Microstructure and High-Temperature Wear Behavior of SiMo Ductile Iron

AbstractSiMo ductile irons, typical heat-resistant materials, are subjected to varied wear environments during operation in high-temperature applications. SiMo ductile iron castings of different thicknesses were cast in investment and greensand molds, achieving a wide range of cooling rates. The present work aims to investigate the effect of the cooling rate and alloying elements (Cr, V, and Ni) on the microstructure and the abrasive wear behavior of these grades of SiMo ductile iron at high-temperature 700 °C under different loads. Thermodynamic calculations were used to propose the phase diagrams, critical transformation temperatures, and phase volume fractions in all SiMo alloys by using the Thermo-Calc software then verified by and Differential Scanning Calorimetry (DSC). The microstructure of unalloyed SiMo ductile cast iron consists of graphite nodules and carbides embedded in the precipitates at the grain boundary regions in a ferrite matrix. The alloyed SiMo microstructure contains nodular graphite and the carbides promoted by the alloying elements (Cr and V). The alloyed SiMo alloys exhibit higher wear resistance than unalloyed ones. These wear results support that the microstructure plays a chief role in wear loss. The combination of M6C, VC, and M7C3 carbides embedded in a ferrite-pearlite matrix (alloyed SiMo) seems to be more resistant to wear than the ferritic matrix with lamellar pearlite and eutectic M6C carbides (unalloyed SiMo).

PHYSICAL-CHEMICAL MODELING AND INVESTIGATION OF THE “HIGH-ENTROPY METAL MATRIX / TiC” SYSTEM COMPONENTS INTERACTION

The research carried out is aimed at developing the scientific basis for obtaining new composite materials based on high-entropy alloys, as well as developing the basic principles of processing and operation of such materials. It was necessary to conduct a theoretical and experimental study of the physical-chemical processes occurring during the interaction of high-entropy alloys with reinforcing TiC particles, as well as to study the effect of temperature and composition of interacting phases on the interaction process and its results. Thermodynamic and kinetic modeling of the interaction processes of the matrix components of high-entropy alloys based on the Cantor alloy (FeCoCrNiMn), including titanium and carbon with the formation of titanium carbide was carried out. Modern modeling approaches were used, which makes it possible to implement modern software. In particular, thermodynamic modeling using methods developed within the framework of the Calphad approach was carried out. Thermo-Calc software (includingTC-PRISMA kinetic modeling software) and FactSage software were used in the research process. An experimental study of the composition and structure of samples of TiC-reinforced metal matrix materials (using electron microscopy, X-ray spectral microanalysis and XRD) was also carried out. The distribution of various elements in the microstructure of materials and their phase composition were investigated. Comparison of the simulation results with experimental data allowed to make conclusions about the qualitative adequacy of thermodynamic and kinetic models of phase equilibria and phase transformations occurring during the formation, possible heat treatment and operation of TiC-reinforced metal matrix materials at high temperatures to the observed experimental data.

Influence of magnesium treatment on inclusions and primary carbides in As-cast H13 die steel

In this study, the inclusions and primary carbides in H13 hot-work tool steel were investigated, both with and without magnesium treatment, utilizing various analytical techniques such as optical microscope (OM), scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and quantitative analysis methods. Furthermore, the experimental results were compared with the calculations obtained from Thermo-Calc software. The results revealed that as we move from the edge to the center of the steel, the equivalent diame-ter of inclusions increased. However, upon adding magnesium to the steel, the size of inclusions decreased, while the number of inclusions per unit area increased. The primary carbides found in H13 steel consisted of vanadium-rich MC carbides and molybdenum-chromium-rich M2C carbides. The addition of magnesium had a significant impact on the size of these primary carbides. The presence of MgAl2O4 particles acted as heterogeneous nuclei, providing nucleation sites that induced smaller sizes and more uniform distribution of primary carbides. Furthermore, it was observed that the banded segregation in the annealed microstructure became more uniform after magnesium treatment, leading to an improvement in the banded segregation.

Effect of copper addition on precipitation behaviors and mechanical properties of Mg-Zn-Cu alloys with respect to high zinc

The current work deals with the precipitation behaviors and mechanical properties of the high zinc content of the Mg-Zn-Cu system alloys using gravity casting. Differential scanning calorimetry (DSC) was conducted to describe the solidification process and precipitation behaviors. Thermodynamic calculations were carried out to determine the precipitation conditions using the Thermo-calc software. The microstructures were characterized by an optical microscope (OM), scanning electron microscope (SEM), electron probe micro analysis (EPMA), transmission electron microscopy (TEM), and confocal laser scanning microscope (CLSM). Tensile tests and micro-hardness tests were applied to investigate the mechanical properties. The results substantiated that the MgZnCu phase precipitates in Cu-containing alloys and that the precipitate content, as well as the precipitate temperature, increased with the Cu content from 0 to 3 wt.% according to the thermodynamic calculations and the DSC results. The measured micro-hardness of the alloy was 53.2, 57.9, 55.8, and 52.5 VHN, respectively. The ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) revealed a λ-like trend of the alloys, and Mg-7Zn-1Cu alloy exhibits the optimum tensile properties with the UTS of 258.9 MPa, YS of 126.2 MPa, and the EL of 14.2%.

Optimization of the three-component Al-Fe-Si system composition

Three-component Al-Fe-Si systems with an equiatomic composition are high-strength alloys that are poorly resistant to plastic deformation. To increase the material ductility, a phase diagram of the Al-Fe-Si ternary system was constructed using ThermoCalc software. The conditions for the formation of the AL8FE2SI phase, which is an α-phase and has a hexagonal lattice, have been identified. At solidus temperatures, α-AL8FE2SI and β-AL9FE2SI2 are competitive. The conditions for the developing a single-phase region consisting of 97% α-AL8FE2SI have been identified. α-AL8FE2SI is a high-temperature phase; the system will perceive plastic deformation in the temperature range of 675–612 °C, with further phase conversion upon cooling.

Effect of Sintering Temperature on Phase Formation and Mechanical Properties of Al–Cu–Li Alloy Prepared from Secondary Aluminum Powders

Aluminum and its alloys are very versatile materials used in a wide range of applications due to the initial characteristics of pure aluminum and the combination of properties obtained from its blend with other elements. Considering that aluminum is the second-most-produced metal after steel, and that its production will increase over time based on the demand to produce products through conventional and additive methodologies, this will lead to an increase in the energy consumed as well as the footprint of carbon generated. It is for this reason that the generation of competitive aluminum alloys must be approached from secondary sources (recycling). To address these environmental issues, in this work, 2070 aluminum alloy (AA2070) samples were manufactured using secondary aluminum powder and compared with the primary aluminum source. The samples were compacted at 700 MPa and sintered at a different range of temperatures between 525 °C and 575 °C. The study includes thermodynamic modeling, microstructure, and mechanical characterization. Microstructure and phases characterization were carried out via scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, respectively, whereas the mechanical characterization comprised relative density evaluation, hardness, and flexion tests. Results were compared with the calculation of phase stability using Thermo-Calc software 2020a. Based on the results obtained, it can be concluded that the secondary AA2070 optimal sintered temperature, where the components raised the highest mechanical properties and effective relative density range, is 575 °C. Furthermore, the recycled alloys have similar relative densities and flexural strengths than the corresponding alloys made from primary aluminum powder.

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.

Hydrogen trapped by the precipitates of microalloying elements (Nb, Ti, and V) in low C ferritic steels: A quantitative analysis

A quantitative approach is presented here that studies the H trapped by the precipitates of microalloying elements (Nb, Ti, and V) in low C ferritic steels. Three model steels, each with one of the three microalloying elements, were prepared in the laboratory and subjected to aging treatment after solutionizing to achieve precipitates in ferrite. The precipitation reactions in the alloys were simulated using the TC-PRISMA module in Thermo-Calc software (databases: TCFE11 and MOBFE6) and subsequently validated using a small-angle neutron scattering (SANS) study. The H trapping abilities in the aged alloys were estimated after saturation H charging using electrochemical means and correlated with the volume fraction, number density, size, and interface character of the precipitates (all estimated using SANS). The relative H trapping ability of the precipitates was estimated as TiC > NbC > VC. The optimum aging conditions to achieve the best H trapping abilities were identified. Moreover, the maximum number of H atoms that can be trapped at the precipitate-ferrite interfaces were estimated based on the geometric considerations using SANS-estimated precipitate quantifications for each alloy. Subsequently, it was argued that the total quantity of trapped H by these precipitates can be explained if H remains trapped within the precipitate bodies in addition to those trapped at interfaces.

Diffusivities and atomic mobilities in bcc Ti–V–Mo alloys

In pursuit of a comprehensive exploration into the diffusion kinetics of bcc Ti–V–Mo alloys, sixteen sets of diffusion couples were prepared within the bcc phase of Ti–V–Mo alloys. These diffusion couples were subjected to annealing at 1373 K and 1473 K. Composition profiles were obtained by means of the electron probe micro-analysis technique (EPMA). The calculation of diffusivities in bcc Ti–V–Mo alloys was performed using the Whittle-Green and Hall methods. Based on available thermodynamic descriptions, the atomic mobility parameters of the bcc Ti–V–Mo system were assessed by using the DICTRA module of the Thermo-Calc software. A comparison is made between the simulated composition-distance curve and the diffusion path with the experimental values, revealing a significant level of concordance.

Effects of Nb addition on the microstructure and low-cycle fatigue properties of heat-resistant stainless steel

This study aims to improve the quality and durability of materials used in turbocharger housing, particularly to limit the degradation of automobile engine parts. As a result, niobium (Nb)-bearing heat-resistant cast austenitic stainless-steel samples have been explored. Two distinct steel samples, denoted as Alloy-A (with 0 wt.% Nb) and Alloy-B (with 1.5 wt.% Nb), were fabricated by centrifugal casting for investigating the effects of Nb content on the corresponding microstructure and low-cycle fatigue properties of these samples. The phases formed within these alloys were predicted by thermodynamic calculations using the Thermo-Calc software, with the results aligning well with the experimental results. The addition of Nb promoted the formation of niobium carbide, resulting in increased hardness and greater area fraction of the carbides present in the steel samples. Alloy-B displayed enhanced high-temperature strength over Alloy-A, while the low-cycle fatigue resistances of the two alloys were similar. Fatigue cracks predominantly initiated at the outer surface of the specimens, mainly in the carbide regions, due to the mismatch between the matrix and carbide hardness. This paper is the first to report the effect of Nb addition on the microstructure and low-cycle fatigue properties of heat-resistant cast austenitic stainless steel.

Influence of Si and Mo on the Sigma-Phase Precipitation in S32750 Super Duplex Stainless Steel Slab

In this study, we investigated the effect of Si and Mo on the sigma-phase precipitation in S32750 super duplex stainless steel slab. The activity for Mo with increasing Si and Mo was calculated by the Wagner formula, and the equilibrium solidification phase diagrams of S32750 duplex stainless steels with different Si and Mo contents were calculated using the thermo-calc software. The sigma phase precipitated mainly at ferrite/austenite phase boundaries and grew up towards the interior of ferrite phase in S32750 SDSS slab. The area fraction and size of the sigma phases significantly increased with increasing Mo content and Si content. Also, the increment in Mo and Si content affected the Mo concentration in sigma phase. The sample（Mo:3.4%,Si：0.3%） had a lowest sigma-phase area fraction of 2.84% and had lowest Mo content in σ phase.The calculation results showed that the increase of Mo and Si content increased the initial precipitation temperature and maximum precipitation amount of σ phase in S32750 SDSS equilibrium phase diagram. The activity of Mo also increased with increasing Si content and Mo content. That is, Mo and Si elements promoted the precipitation of σ phase.

Study Of the Effect of Titanium Additions on The Mechanical and Corrosion Properties of AISI 316 Powder Metallurgical Steel

Context: Powder metallurgy uses metallic and/or non-metallic powders that, through mixing, compacting, and sintering operations, allow obtaining large series of products. In austenitic stainless steels, Cr23C6-type carbides can precipitate at temperatures between 450 and 950 °C. When this occurs, the steel is susceptible to being attacked at its grain boundaries by a phenomenon called sensitization. Titanium is added as a ‘stabilizer’ because it has a greater affinity with carbon for the formation of species at a temperature of approximately 900 ºC, and, during cooling, it consumes the carbon forming MC-type carbides, inhibiting the precipitation of Cr23C6. Method: The composition and morphology of the powders were characterized, leading to the formulation of an alloy matrix consisting of a mixture of AISI 316 steel powders of two different particle-size distributions in a proportion that produced the highest density and the lowest porosity in the sintered material. Titanium was added at two levels (0,4 and 1,0 wt%), and sintering was carried out with nitrogen. The corrosion rate was determined by potentiodynamic polarization. Vickers hardness and pin-on-disk wear tests were performed. The stages were complemented with a microstructural analysis. Results: The addition of 0,4 wt% of titanium decreased the steel’s rate of corrosion, albeit in the absence of passivation. The microstructure consists of austenite, ferrite, and TiC precipitates. The addition of 1,0 wt%Ti showed an increase in the corrosion rate, with a microstructure containing austenite, ferrite, TiC carbides, and the Laves ɳ-Fe2Ti phase. Conclusions: The results were compared against thermodynamic simulations in the Thermo-Calc software, which were consistent with the microstructural analysis, showing the phenomena of stabilization as well as the precipitation of intermetallic phases and highlighting the importance of establishing strict controls in the formulation of powder metallurgical alloys due to the transformations that can take place due to the effect of the thermal cycles of the process.

Computational and experimental investigation of a new non equiatomic FCC single-phase Cr15Cu5Fe20Mn25Ni35 high-entropy alloy

The structural, mechanical, and thermal properties of a new non-equiatomic face-centered cubic (FCC) structured high entropy alloy (HEA) were examined computationally using density functional theory (DFT) calculations and validated experimentally. To identify potential single phase HEA candidates, the composition space of the CrCuFeMnNi alloy system, including 1451 alloys, was investigated using the CALculation of PHAse Diagrams (CALPHAD) method and Thermo-Calc software. The CALPHAD approach successfully predicted an FCC single-phase Cr15Cu5Fe20Mn25Ni35 alloy. Elastic constants and thermal properties of the Cr15Cu5Fe20Mn25Ni35 HEA were determined through DFT calculations using a 100-atom supercell. To validate the DFT calculations, HEA samples were prepared by the arc melting technique, and X-ray diffraction (XRD) analysis confirmed a single-phase FCC structure.The DFT calculated elastic constants values satisfied the Born stability conditions for stability of a cubic crystal structure. Pugh's theory indicated that this alloy exhibits ductility and metallic behavior due to its B/G ratio exceeding 1.75 and positive Cauchy pressure. Additionally, Poisson's ratio exceeded 0.26, further confirming its ductile nature. Experimental tests confirmed these findings by measuring bulk modulus, shear modulus, Young's modulus, and Poisson's ratio. The calculated CV values showed good agreement with experimental data at different temperatures. The linear coefficient of thermal expansion increased rapidly at lower temperatures before becoming linear. Both XRD as well as DFT calculations yielded similar lattice constant results for this HEA. These findings provide insights into various properties of the Cr15Cu5Fe20Mn25Ni35 HEA, including its structural stability, mechanical behavior and thermal characteristics.

Structural and mechanical investigation of a TiAl2 based alloy: A combined theoretical and experimental study

In this study, Zr and Nb doped TiAl2 alloy (Ti-43Al-6Zr-2Nb (wt.%)) has been investigated with the support of thermodynamic simulation by the ThermoCalc software, followed by production with vacuum induction melting. Ti-43Al-6Zr-2Nb (wt.%) alloy is revealed as thermodynamically stable by ThermoCalc. Dendritic with lamellar phase mixtures microstructure of TiAl and TiAl2 has been obtained by X-Ray diffraction and scanning electron microscopy studies. The resultant phases match well with phase diagram of Ti-43Al-6Zr-2Nb (wt.%) alloy drawn with ThermoCalc software. TiAl2 brittle nature due to high hardness and elastic modulus have been diminished by Zr and Nb addition. Findings of this study contribute a valuable insight for development of multicomponent TiAl2 based alloys.