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  • 1. Abu-Odeh, A.
    et al.
    Galvan, E.
    Kirk, T.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chen, Q.
    Mason, P.
    Malak, R.
    Arróyave, R.
    Efficient exploration of the High Entropy Alloy composition-phase space2018In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 152, p. 41-57Article in journal (Refereed)
    Abstract [en]

    High Entropy Alloys (HEAs), Multi-principal Component Alloys (MCA), or Compositionally Complex Alloys (CCAs) are alloys that contain multiple principal alloying elements. While many HEAs have been shown to have unique properties, their discovery has been largely done through costly and time-consuming trial-and-error approaches, with only an infinitesimally small fraction of the entire possible composition space having been explored. In this work, the exploration of the HEA composition space is framed as a Continuous Constraint Satisfaction Problem (CCSP) and solved using a novel Constraint Satisfaction Algorithm (CSA) for the rapid and robust exploration of alloy thermodynamic spaces. The algorithm is used to discover regions in the HEA Composition-Temperature space that satisfy desired phase constitution requirements. The algorithm is demonstrated against a new (TCHEA1) CALPHAD HEA thermodynamic database. The database is first validated by comparing phase stability predictions against experiments and then the CSA is deployed and tested against design tasks consisting of identifying not only single phase solid solution regions in ternary, quaternary and quinary composition spaces but also the identification of regions that are likely to yield precipitation-strengthened HEAs.

  • 2.
    Bigdeli, Sedigheh
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ehtehsami, Hossein
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chen, Qing
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    New description of metastable hcp phase for unaries Fe and Mn: Coupling between first-principles calculations and CALPHAD modeling2016In: Physica Status Solidi B, ISSN 1521-3951, no 9, p. 1830-1836Article in journal (Refereed)
    Abstract [en]

    The main focus in developing the third generation of CALPHADdatabases is to model thermodynamic properties of materialsby using models which are more physically based andvalid down to 0K. First-principles calculations are helpful tochoose and validate those models. Reliable calculation results,for example, at very low temperatures or on metastable systemsreveal physical facts which might be inaccessible by experiments.Following our earlierwork for modeling thermodynamicproperties of pure elements (i.e., Fe and Mn) in third-generationCALPHAD databases, the (hcp) phase was modeled as ametastable phase in the present work. Although hcp phase isjust observed in these two elements under ultra-high pressure, inthe binary Fe–Mn this phase is metastable at ambient temperaturesand pressures. Therefore, it should be properly modeled inunaries for later optimization of binary systems. Based on densityfunctional theory (DFT) calculations, the magnetic groundstate and the magnetic properties of -Fe, -Mn, and their binarysolution phase were calculated. It was found that -Fe is antiferromagnetic(type II) while -Mn has a paramagnetic groundstate. Accordingly, magnetic contributions to thermodynamicproperties were accurately modeled. Moreover, by means ofthe extrapolation of experimental data for the thermodynamicproperties of binary systems and high-pressure data for unaries,the metastable hcp phases at ambient pressure were modeledfor the third-generation CALPHAD database, consistently withother stable phases in the elements Fe and Mn.

  • 3.
    Bigdeli, Sedigheh
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    On the third-generation Calphad databases: An updated description of Mn2015In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 252, no 10, p. 2199-2208Article in journal (Refereed)
    Abstract [en]

    Aiming for better extrapolations and predictabilities of thermodynamic properties of materials, new thermodynamic models are implemented in the third-generation Calphad databases. In these models, each term contributing to the Gibbs energy has an explicit physical meaning. Furthermore, descriptions of thermodynamic properties of materials are valid from 0K up to high temperatures far above the melting point. As a starting point for the development of large self-consistent third-generation database, the new models in the present work are applied to the unary manganese system. Taking into account both the calculated first principles results and experimental data, thermodynamic model parameters are evaluated. Thermodynamic properties predicted using this description, agree very well with available data. The calculated properties vary smoothly in the whole temperature range, which is another important improvement compared to the second-generation databases.

  • 4. Bratberg, J.
    et al.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Kjellqvist, L.
    Engström, A.
    Mason, P.
    Chen, Q.
    The Development and Validation of a New Thermodynamic Database for Ni-Based Alloys2012In: Proceedings of the International Symposium on Superalloys 2012, John Wiley & Sons, 2012, p. 803-812Conference paper (Refereed)
    Abstract [en]

    Thermodynamic databases developed using the CALPHAD method has been successfully applied to the modeling and simulation of Ni based superalloys for more than fifteen years. Such databases when combined with suitable software, such as Thermo-Calc, can be used for accelerating alloy design as well as improving understanding of existing alloys in terms of their processing and in-service behavior. Additionally, such databases are also essential to the modeling of microstructural evolution using methods such as phase field or mean field approaches. A new thermodynamic database, TCNI6, has been developed for Ni-based superalloys based on the critical evaluation, using the CALPHAD method, of all the constituent binary systems across their full range of composition and many of the ternary systems containing Ni, as well as a number of other key ternary systems. The database has also been validated where possible against higher order systems as well. Together with the new mobility database, MOBNI3, which contains descriptions for the atomic mobility for respectively the γ (Al), γ' (Ll2), α (A2), β (B2) and liquid phases, TCNI6 can be used with software such as DICTRA to predict different kinetic aspects taking all relevant phases into account, e.g. the simulation of interdiffusion across Ni-based coatings. A new user friendly computational tool, TC-PRISMA, which simulates the kinetics of precipitation processes, is demonstrated utilizing these new databases and combined with interface property data. Engineering applications of precipitation modelling are validated against experimental data.

  • 5. Brennhaugen, David D. E.
    et al.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Louzguine-Luzgin, Dmitri V.
    Arnberg, Lars
    Aune, Ragnhild E.
    Predictive modeling of glass forming ability in the Fe-Nb-B system using the CALPHAD approach2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 707, p. 120-125Article in journal (Refereed)
    Abstract [en]

    Accurate values needed for the most commonly used indicators of good Glass Forming Ability (GFA) in alloys, i.e. the liquidus (T-l), crystallization (T-x) and glass transition (T-g) temperatures, are only available after successful production of the metallic glass of interest. This has traditionally made discovery of new metallic glasses an expensive and tedious procedure, based on trial-and-error methodology. The present study aims at testing the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) approach for predicting GFA in the Fe-Nb-B system by the use of the Thermo-Calc software and the thermodynamic database TCFE7. The melting temperatures and phase stabilities were calculated and combined with data for an atomic size mismatch factor, lambda, in order to identify and map potential high-GFA regions. Selected compositions in the identified regions were later produced by suction casting and melt spinning, and the potential success verified using X-Ray Diffraction (XRD). Differential Scanning Calorimetry (DSC) was also used to compare thermodynamic calculations for the model predictions, and evaluate standard GFA indicators. The model is found to fit well with literature data, as well as predict new bulk glassy compositions at and around Fe70.5Nb7B22.5. These results show promise in further predictive use of the model.

  • 6.
    Chen, Hai-Lin
    et al.
    Thermocalc Software AB, S-16967 Solna, Sweden..
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermocalc Software AB, S-16967 Solna, Sweden.
    Chen, Qing
    Thermocalc Software AB, S-16967 Solna, Sweden..
    Database development and Calphad calculations for high entropy alloys: Challenges, strategies, and tips2018In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 210, p. 279-290Article in journal (Refereed)
    Abstract [en]

    The development of a reliable multicomponent thermodynamic database for high entropy alloys (HEAs) is a daunting task and it faces new challenges comparing to the development of databases for conventional single principal element alloys, such as the assessment of a large number of ternary systems, the proper estimation of phase stability within metastable compositional and temperature ranges, and the reasonable extrapolation into higher order systems. We have recently established a thermodynamic database (TCHEA1) especially for HEAs within a 15-element framework. This work highlights the usage of high throughput density functional theory (OFT) calculations for validating and refining the binary and ternary parameters of the solid solution phases, and having a more reliable extrapolation into metastable regions and higher order systems. TCHEA1 consists of 105 binaries and 200 ternaries and contains nearly all the stable solution phases and intermetallic compounds in each of the assessed systems. Together with Thermo-Calc, this database enables us to predict the stability of the desired multicomponent solid solution relative to intermetallic compounds and other solid solutions. Calculation examples are presented not only for case studies but also for bridging the knowledge gap between Calphadian and people who do not have a background of the Calphad approach.

  • 7.
    Chen, Kaixuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chen, Xiaohua
    Univ Sci & Technol Beijing, State Key Lab Adv Met & Mat, Beijing 100083, Peoples R China..
    Wang, Zidong
    Univ Sci & Technol Beijing, Sch Mat Sci & Engn, Beijing 100083, Peoples R China..
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology. KTH, School of Industrial Engineering and Management (ITM), Centres, Brinell Centre - Inorganic Interfacial Engineering, BRIIE.
    Optimization of deformation properties in as-cast copper by microstructural engineering. Part I. microstructure2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 763, p. 592-605Article in journal (Refereed)
    Abstract [en]

    The microstructural features required to optimize both the strength and ductility of copper are investigated by examining the as-cast pure Cu and Cu-(1.0e3.0)Fe-0.5Co and Cu-1.5Fe-0.1Sn (wt %) alloys. Uniaxial tensile tests show that (Fe, Co)- or (Fe, Sn)-doping improves both the strength and ductility of pure copper. The microstructure evolution with Fe, Co, or Sn doping is characterized by using optical and scanning and transmission electron microscopies. The effects of Fe, Co, and Sn doping on the microstructure clearly show that (i) iron-rich nanoparticles are dispersed inside the grains. The spherical nanoparticles grow in size with increasing Fe content, and when the Fe content exceeds 2.0 wt %, the particles transition into a petal-like morphology. (ii) The microstructure of the alloys (grain size and morphology) is notably influenced by the Fe and Co contents, and the grain size is reduced from an average of 603 mu m in pure Cu to an average of 26 mm in the Cu-3.0Fe-0.5Co alloy. (iii) The addition of 1.5wt % Fe and 0.1wt % Sn dramatically reduces the grain size to an average of 42 mu m, and this reduction is correlated with the appearance of smaller spherical iron-rich nanoparticles. The evolution mechanisms of the iron-rich nanoparticles and grain structure under the alloying effect are discussed.

  • 8.
    Dilner, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Kjellqvist, Lina
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Improving Steel and Steelmaking - Computational Thermodynamics using a Sulphide and Oxide databaseManuscript (preprint) (Other academic)
  • 9.
    Dilner, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Scania CV AB, SE-15187 Sodertalje, Sweden..
    Kjellqvist, Lina
    Thermocalc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermocalc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Improving Steel and Steelmakingan Ionic Liquid Database for Alloy Process Design2018In: INTEGRATING MATERIALS AND MANUFACTURING INNOVATION, ISSN 2193-9764, Vol. 7, no 4, p. 195-201Article in journal (Refereed)
    Abstract [en]

    The latest development of a thermodynamic database is demonstrated with application examples related to the steelmaking process and steel property predictions. The database, TCOX, has comprehensive descriptions of the solution phases using ionic models. More specifically, applications involving sulphur and oxygen, separately as well as combined, are presented and compared with relevant multi-component experimental information found in the literature. The over-all agreement is good.

  • 10.
    Dilner, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Lu, Qi
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics. Thermocalc Software AB, Sweden.
    Xu, Wei
    van der Zwaag, Sybrand
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Process-time Optimization of Vacuum Degassing Using a Genetic Alloy Design Approach2014In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 7, no 12, p. 7997-8011Article in journal (Refereed)
    Abstract [en]

    This paper demonstrates the use of a new model consisting of a genetic algorithm in combination with thermodynamic calculations and analytical process models to minimize the processing time during a vacuum degassing treatment of liquid steel. The model sets multiple simultaneous targets for final S, N, O, Si and Al levels and uses the total slag mass, the slag composition, the steel composition and the start temperature as optimization variables. The predicted optimal conditions agree well with industrial practice. For those conditions leading to the shortest process time the target compositions for S, N and O are reached almost simultaneously.

  • 11.
    Dilner, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Thermodynamic assessment of the Mn-S and Fe-Mn-S systems2015In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 48, p. 95-105Article in journal (Refereed)
    Abstract [en]

    The Fe-Mn-S system is of great importance for the steelmaking process. As part of the work for the development of a large self-consistent thermodynamic database for such applications, the aim of the present assessment was to obtain a thermodynamic description of the Fe-Mn-S system using the ionic two-sublattice model for the liquid. Previous compatible descriptions of all unaries as well as two of the constituent binaries, Fe-Mn and Fe-S, were accepted. The third binary, Mn-S, was assessed in this work. Ternary parameters were optimised for the liquid, the alabandite, the pyrrhotite and the pyrite phases. Calculations using the present description agree well with experimental data.

  • 12.
    Gunasekara, Saman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Bigdeli, Sedigheh
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Chiu, Justin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Thermodynamic assessment of binary erythritol-xylitol phase diagram for phase change materials design2018In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 60, p. 29-36Article in journal (Refereed)
    Abstract [en]

    Here, the erythritol-xylitol binary system was thermodynamically optimized based on available experimental phase equilibrium data, to explore compositions suitable as phase change materials (PCMs) for thermal energy storage (TES). A previous experimental study revealed that erythritol-xylitol was a partially isomorphous system with a eutectic. In the thermodynamic evaluation, the CALPHAD method was employed coupling the phase diagram and thermodynamic property information. There, both unary and binary systems’ experimental data were taken into account, and all phases were described using the substitutional solution model. Finally, a self-consistent thermodynamic description for the erythritol-xylitol system was achieved. The calculated eutectic point is at 76.7 °C and 26.8 mol% erythritol, agreeing well with the experimental data. The calculated phase diagram better-verifies the systems’ solidus and the solvus, disclosing the stable phase relations. Based on the Gibbs energy minimization, phase diagrams can be predicted for the binary and higher order systems, provided the component subsystems are thermodynamically assessed beforehand. In conclusion, to move forward beyond e.g. non-isomorphous simple eutectic systems, methods using Gibbs free energy minimization from a fundamental point-of-view such as CALPHAD are essential.

  • 13.
    Gunasekara, Samman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Bigdeli, Sedigheh
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Thermodynamic Assessment of Binary Erythritol-Xylitol Phase Diagram for Phase Change Materials DesignManuscript (preprint) (Other academic)
    Abstract [en]

    Here, the experimental phase equilibrium data of the erythritol-xylitol system were thermodynamically optimized, to explore compositions suitable as phase change materials (PCMs) for thermal energy storage (TES). A previous experimental study revealed that erythritol-xylitol was a partially isomorphous system with a eutectic. In the thermodynamic evaluation, the CALPHAD method was employed coupling the phase diagram and thermodynamic property information. There, both unary and binary systems’ experimental data were taken into account, and all phases were described using the substitutional solution model. Finally, a self-consistent thermodynamic description for the erythritol-xylitol system was achieved. The calculated eutectic point is at 76.7 °C and 26.8 mol% erythritol, agreeing well with the experimental data. The calculated phase diagram better-verifies the systems’ solidus and the solvus, disclosing the stable phase relations. Based on the Gibbs energy minimization, phase diagrams can be predicted for the binary and higher order systems, provided the component subsystems are thermodynamically assessed beforehand. In conclusion, to move forward beyond e.g. non-isomorphous simple eutectic systems, methods using Gibbs free energy minimization from a fundamental point-of-view such as CALPHAD are essential.

  • 14. He, J. Y.
    et al.
    Wang, H.
    Wu, Y.
    Liu, X. J.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nieh, T. G.
    Lu, Z. P.
    Precipitation behavior and its effects on tensile properties of FeCoNiCr high-entropy alloys2016In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 79, p. 41-52Article in journal (Refereed)
    Abstract [en]

    In this work, we present a systematic study on the precipitation behavior and mechanical properties of a FeCoNiCr-based high-entropy alloy alloyed with dilute amounts of Ti and Al, (FeCoNiCr)(100-x-y)TixAly (where x = 1-3, y = 4-9 at.%). It was found that, upon aging, nano-sized L1(2)-Ni-3(Ti, Al) particles are formed within grains, whilst L2(1)-(Ni, Co)(2)TiAl Heusler particles are formed mainly along grain boundaries. The relative thermal stability of the two phases were studied at different aging temperatures (700-900 degrees C) with various durations of time (up to 48 h) and the results were directly compared with Thermo-talc calculations. Tensile tests were also conducted on alloys aged under different conditions. The measured properties, including strength and ductility, were correlated with the microstructure of aged (FeCoNiCr)(100-x-y)TixAly alloys, with particular attention on the distribution and morphology of the two kinds of precipitate. Whereas both phases could contribute to the strengthening of the alloys via either Orowan bowing or particle shearing mechanism, the brittle (Ni, Co)(2)TiAl Heusler phase was found to mainly affect the tensile plasticity. A simple composite model was proposed to describe the plastic strain of alloys. Based on observed microstructure and its corresponding mechanical performance, the alloy with the composition of (FeCoNiCr)(94)Ti2Al4, when aged between 700 and 800 degrees C, gives the best balanced strength/ductility properties.

  • 15.
    Hillert, Mats
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Kjellqvist, Lina
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sundman, Bo
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Parameters in the compound energy formalism for ionic systems2009In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 33, no 1, p. 227-232Article in journal (Refereed)
    Abstract [en]

    The compound energy formalism, CEF, involves many model parameters. They are evaluated to give the best fit to the experimental information. The optimisation is simpler if less parameters need to be adjusted.The maximum number of independent parameters that can be evaluated depends on the information available. The best choice of parameters is first discussed for simple ionic substances with an internal variable, then for solutions of two or four such substances.

    To reduce the number of parameters, independent parameters are conveniently defined as combinations of primary model parameters. That may be possible when there is an internal variable,which can take only one value, the value that minimizes the Gibbs energy. Such combinations may be regarded as the true optimisation parameters and they may be used actively during an optimisation. The present discussion deals with substances with an internal variable and mixtures, which may have more than one internal variable.

    The conclusions apply equally well to non-ionic systems if the information is limited to stoichiometric compositions. The optimisation parameters should then be defined for stoichiometric overall compositions.

  • 16.
    Holmström, Erik
    et al.
    Sandvik Coromant R&D, SE-12680 Stockholm, Sweden..
    Lizarraga, Raquel
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Linder, David
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Salmasi, Armin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Kaplan, Bartek
    Sandvik Coromant R&D, SE-12680 Stockholm, Sweden..
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermocalc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermocalc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. ppsala Univ, Div Mat Theory, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    High entropy alloys: Substituting for cobalt in cutting edge technology2018In: Applied Materials Today, ISSN 2352-9407, Vol. 12, p. 322-329Article in journal (Refereed)
    Abstract [en]

    Cemented carbide, also known as hard metal, is one of the most outstanding composite engineering materials since its commercial introduction in the 1920s. The unique combination of strength, hardness and toughness makes cemented carbides highly versatile materials for the most demanding engineering applications. In their simplest form, these materials are composites of tungsten carbide (WC) grains that are cemented with a ductile metallic binder phase, typically cobalt. However, despite the superiority of Co as binder material, there is a long-standing need to find alternative binders due to serious health concerns that have haunted the industry for nearly 80 years. In the present study, we develop a new cemented carbide with a high entropy alloy binder phase (CoCrFeNi) from raw materials to a fully functional, coated and gradient-sintered cutting tool insert. The new hard metal with reduced Co content is designed by using first principles theory and the CALPHAD method. The cutting tool was made by pressing the new hard metal in a standard geometry, sintered to have a thin binder phase enriched surface zone, free from cubic carbides and coated with protective layers of Ti(C,N) and Al2O3. The resulting cutting insert was tested in a real machining operation and compared to a state-of-the-art reference that had Co as binder phase. The cutting tool made of the newly developed cemented carbide has an exceptionally high resistance against plastic deformation at all tested cutting speeds in the machining test, outperforming the reference insert, which shows a linear increase in edge depression when the cutting speed is increased. This result opens up the possibility to utilize the unique properties of high entropy alloys for industrial applications, in particular, as binder phase in new cemented carbides.

  • 17.
    Li, Wei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Lu, Song
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Hu, Qing-Miao
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    The effect of Al on the 475 degrees C embrittlement of Fe-Cr alloys2013In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 74, p. 101-106Article in journal (Refereed)
    Abstract [en]

    Aluminum addition to ferritic stainless steels was found to effectively suppress the deleterious 475 degrees C embrittlement resulting from the phase decomposition in concentrated Fe-Cr alloys. With the aim of revealing the mechanism behind this prosperous phenomenon, here we investigate the effect of Al on the interfacial energy and formation energy of Fe-Cr solid solutions. The interface between the decomposed Fe-rich alpha and Cr-rich alpha' phases carries a positive excess energy, which is of significant importance on determining the process of phase separation. Using ab initio alloy theory, we show that for the alpha-Fe70Cr20Al10/alpha'-Fe100-x-yCryAlx (0 <= x <= 10, 55 <= y <= 80) interface, the Al content (x) barely changes the interfacial energy. However, for the alpha-Fe100-x-yCryAlx/alpha'-Fe10Cr90 (0 <= x <= 10, 0 <= y <= 25) interface, the interfacial energy increases with Al content due to the variation of the formation energies of the Fe-Cr alloys upon Al alloying. Our ab initio results are supported by CALPHAD calculations, and suggest that the beneficial effect of Al on ferritic steels is mainly due to its thermodynamical effect on the alpha' phase.

  • 18.
    Li, Zhou
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Bigdeli, Sedigheh
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chen, Q.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermodynamic evaluation of pure Co for the third generation of thermodynamic databases2016In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951Article in journal (Refereed)
    Abstract [en]

    An updated thermodynamic description of pure Co was obtained by applying new models for the third generation of Calphad databases. In these models, different contributions to the heat capacity, especially the vibrational part, were treated separately, each with a clear physical meaning. More importantly, the phase stabilities of the various allotropes are now physically well defined. Thus, the derived thermodynamic properties vary more reasonably and smoothly from 0K and up. Calculated thermodynamic properties were compared with experimental data and good agreement was obtained. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 19.
    Li, Zhou
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Korzhavy, Pavel
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Thermodynamic re-assessment of the Co-Cr system supported by first-principles calculations2016In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 52, p. 1-7Article in journal (Refereed)
    Abstract [en]

    The phase equilibria and thermochemical properties of the Co-Cr system was re-assessed using the Calphad method with the aid of ab initio calculations. Four solution phases, liquid, bcc, fcc and hcp phases are modeled using the substitutional solution model. The sigma phase, as an intermetallic compound with certain homogeneous composition range, is modeled by a full five sublattices partitioned CEF model. The formation enthalpies of all end-members are obtained from ab initio calculations. The calculated results fit the experimental data reasonably well which indicates that this ab initio aided model is a proper description for the sigma phase.

  • 20.
    Li, Zhou
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    A new thermodynamic description of stable Cr-carbides for the third generation of thermodynamic database2017In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 59, p. 107-111Article in journal (Refereed)
    Abstract [en]

    An updated thermodynamic description of the stable Cr-carbides was obtained by applying the same models as used for the elements within the 3rd generation of thermodynamic databases. The Einstein model was used and a scaling factor was introduced to take into account the coupling effect between the stoichiometry (C to Cr ratio) and the structure of the compound. Using this model we could accurately describe the thermodynamic properties of these stoichiometric compounds using available experimental heat capacity data. The new description is now more physically sound and results in a better agreement with the experimental heat capacity data.

  • 21.
    Li, Zhou
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Thermodynamic Modeling of Pure Co Accounting Two Magnetic States for the Fcc Phase2018In: JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION, ISSN 1547-7037, Vol. 39, no 5, p. 502-509Article in journal (Refereed)
    Abstract [en]

    The thermodynamic functions of the pure Co were assessed using CALPAHD method for the third generation thermodynamic databases. To model the magnetic properties of the cobalt, a two-state magnetic model was accounted for the fcc phase. Calculated results were compared with the experimental information and a good fit to the experimental data was achieved.

  • 22. Lu, Yiping
    et al.
    Gao, Xiaoxia
    Dong, Yong
    Wang, Tongmin
    Chen, Hai-Lin
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Zhao, Yonghao
    Jiang, Hui
    Cao, Zhiqiang
    Li, Tingju
    Guo, Sheng
    Preparing bulk ultrafine-microstructure high-entropy alloys via direct solidification2018In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, no 4, p. 1912-1919Article in journal (Refereed)
    Abstract [en]

    In the past three decades, nanostructured (NS) and ultrafine-microstructure (UFM) materials have received extensive attention due to their excellent mechanical properties such as high strength. However, preparing low-cost and bulk NS and UFM materials remains to be a challenge, which limits their industrial applications. Here, we report a new strategy to prepare bulk UFM alloys via the direct solidification of high-entropy alloys (HEAs). As a proof of concept, we designed AlCoCrxFeNi (1.8 <= x <= 2.0) HEAs and achieved a complete UFM in bulk materials. The compositional requirements for obtaining the formation of the UFM are highly demanding, necessitating the coupling of near eutectic alloy composition and the high temperature decomposition of supersaturated primary and secondary phases. Our strategy provides a low-cost and highly efficient method to prepare bulk UFM alloys, with great potential to accelerate the engineering application of these materials.

  • 23.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Critical Evaluation of Alumino-silicate Systems: Thermodynamic Modeling of Alumina-containing Liquid and Solid Solutions2008 (ed. 1)Book (Other academic)
    Abstract [en]

    Alumino-silicate systems are of great interest for materials scientists and geochemists. Thermodynamic knowledge of these systems is useful in steel and ceramic industries, and for understanding geochemical processes. A popular and efficient approach used to obtain a self-consistent thermodynamic dataset is called CALPHAD. It couples phase diagram information and thermochemical data with the assistance of computer models. The CALPHAD approach is applied in this work to the thermodynamic modelling and assessments of the CaO-Al2O3-SiO2, MgO-Al2O3-SiO2 and Y2O3-Al2O3-SiO2 systems and their subsystems. The compound energy formalism is used for all the solution phases including mullite, YAM, spinel and halite. In particular, the ionic two sub-lattice model is applied to the liquid solution phase.  Based both on recent experimental investigations and theoretical studies, a new species, AlO2-1, is introduced to model liquid Al2O3. Thus, the liquid model corresponding for a ternary Al2O3-SiO2-M2Om system has the formula (Al+3,M+m)P (AlO2-1,O-2, SiO4-4,SiO20)Q , where M+m stands for Ca+2, Mg+2 or Y+3. This model overcomes the long-existing difficulty of suppressing the liquid miscibility gap in the ternary systems originating from the Al2O3-free side during the assessments.  All the available and updated experimental information in these systems are critically evaluated and finally a self-consistent thermodynamic dataset is achieved. The database can be used along with software for Gibbs energy minimization to calculate any type of phase diagram and all thermodynamic properties. Various phase diagrams, isothermal and isoplethal sections, and thermochemical properties are presented and compared with the experimental data. Model calculated site fractions of species are also discussed. All optimization processes and calculations are performed using the Thermo-Calc software package.

  • 24.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermodynamic modelling and assessment of some alumino-silicate systems2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Alumino-silicate systems are of great interest for materials scientists and geochemists. Thermodynamic knowledge of these systems is useful in steel and ceramic industries, and for understanding geochemical processes. A popular and efficient approach used to obtain a self-consistent thermodynamic dataset is called CALPHAD. It couples phase diagram information and thermochemical data with the assistance of computer models. The CALPHAD approach is applied in this thesis to the thermodynamic modelling and assessments of the CaO-Al2O3-SiO2, MgO-Al2O3-SiO2 and Y2O3-Al2O3-SiO2 systems and their subsystems. The compound energy formalism is used for all the solution phases including mullite, YAM, spinel and halite. In particular, the ionic two sub-lattice model is applied to the liquid solution phase. Based both on recent experimental investigations and theoretical studies, a new species, AlO2-1, is introduced to model liquid Al2O3. Thus, the liquid model corresponding for a ternary Al2O3-SiO2-M2Om system has the formula (Al+3,M+m)P (AlO2-1,O-2, SiO4-4,SiO20)Q, where M+m stands for Ca+2, Mg+2 or Y+3. This model overcomes the long-existing difficulty of suppressing the liquid miscibility gap in the ternary systems originating from the Al2O3-free side during the assessments. All the available and updated experimental information in these systems are critically evaluated and finally a self-consistent thermodynamic dataset is achieved. The database can be used along with software for Gibbs energy minimization to calculate any type of phase diagram and all thermodynamic properties. Various phase diagrams, isothermal and isoplethal sections, and thermochemical properties are presented and compared with the experimental data. Model calculated site fractions of species are also discussed. All optimization processes and calculations are performed using the Thermo-Calc software package.

  • 25.
    Mao, Huahai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermocalc Software AB, Rasundavagen 18A, S-16967 Solna, Sweden..
    Chen, Hai-Lin
    Thermocalc Software AB, Rasundavagen 18A, S-16967 Solna, Sweden..
    Chen, Qing
    Thermocalc Software AB, Rasundavagen 18A, S-16967 Solna, Sweden..
    TCHEA1: A Thermodynamic Database Not Limited for "High Entropy'' Alloys2017In: Journal of Phase Equilibria and Diffusion, ISSN 1547-7037, Vol. 38, no 4, p. 353-368Article in journal (Refereed)
    Abstract [en]

    In this paper we report a thermodynamic database which was developed by using the CALPHAD approach. The TCHEA1 database includes 15 chemical elements (Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Ta, Ti, V, W and Zr). It is suitable for the study of Bcc and Fcc HEA systems. The database is constructed based on the thermodynamic assessment of all binary systems and many key ternary systems where almost all possible metastable and stable phases are considered. It is extensively demonstrated in the present work that TCHEA1 gives satisfactory prediction on the phase equilibria in various HEA systems (quaternary to ennead) and wide temperature ranges (liquidus to subsolidus). Thermodynamic stability calculations of simple solid solutions (Bcc and Fcc) and intermetallics (sigma, Laves, l-phase etc.) are validated against the available experimental information in as-cast or as-annealed state. Such CALPHAD database focusing on the modelling of Gibbs energy rather than entropy makes reliable predictions of thermodynamic equilibrium and phase transformation, no matter whether the alloy/system has high entropy or not. Cases with miscibility gap in liquid and solid solutions and second-order phase transition at low temperatures are demonstrated. With the volume data included, TCHEA1 is capable to predict the density and thermal expansion coefficient of HEAs as well. This thermodynamic database is also applicable in process simulations when used together with compatible kinetic databases.

  • 26.
    Mao, Huahai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Fabrichnaya, Olga
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sundman, Bo
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermodynamic assessment of the MgO-AL(2)O(3)-SiO2 system2005In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 20, no 4, p. 975-986Article in journal (Refereed)
    Abstract [en]

    Thermodynamic properties of the phases in the MgO-Al2O3-SiO2 system were assessed, resulting in a set of self-consistent thermodynamic data. The two ternary Compounds, cordierite and sapphirine, were optimized from subsolidus reactions. The liquid phase was described by the ionic two-sublattice model with a new species AlO2-1 yielding the formula (Al+3,Mg+2)(p)(AlO2-1 O-2,SiO4-4,SiO2o)(Q). Projection of the liquidus surface was calculated. Various isothermal and isoplethal sections were compared with the experimental data.

  • 27.
    Mao, Huahai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Hillert, Mats
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Sundman, Bo
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Thermodynamic assessment of the CaO-Al2O3-SiO2 system2006In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 89, no 1, p. 298-308Article in journal (Refereed)
    Abstract [en]

    The CaO-Al2O3-SiO2 system has been assessed with the CALP-HAD technique, based on recent assessments of its binary systems. A new species AlO2-1 was introduced for modeling liquid Al2O3. The ternary liquid phase was described using the ionic two-sublattice model as (Al+3, Ca+2)(p) (AlO2-1, O-2, SiO4-4 SiO20)(Q). The available experimental data were critically examined and a self-consistent set of thermodynamic descriptions was obtained. Various phase diagrams and property diagrams, including isothermal sections, isoactivity lines, and a projection of the liquidus surface, are presented. Information on viscosity seems to support the use of the AlO2-1 species.

  • 28.
    Mao, Huahai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Thermodynamic reassessment of the Si3N4-AlN-Al2O3-SiO2 system - Modeling of the SWON and liquid phases2007In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 31, no 2, p. 269-280Article in journal (Refereed)
    Abstract [en]

    The technically important quasi-ternary section Si3N4-AlN-Al2O3-SiO2 of the Si-Al-O-N system has been then-nodynamically reassessed. Improved descriptions for the Gibbs energies of the beta and O'-sialon phases are applied. Different modelings according to the different behaviors of the reciprocal system within the beta-sialon phase are discussed. The liquid phase is modeled with a new formula based on the ionic twosublattice model. The thermodynamic properties of the sialon phases are discussed and various phase diagrams are presented. The self-consistent thermodynamic dataset is useful for the computer simulation of sialon synthesis. Some examples of such applications are illustrated.

  • 29.
    Mao, Huahai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Fabrichnaya, Olga
    Thermodynamic assessment of the Y2O3-Al2O3-SiO2 system and its subsystems2008In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 32, no 2, p. 399-412Article in journal (Refereed)
    Abstract [en]

    Phase equilibria and thermodynamic properties at I bar in the Y2O3-Al2O3-SiO2 ternary system and its constituent binaries Y2O3-Al2O3 and Y2O3-SiO2 have been reevaluated using the CALPHAD approach. The liquid phase is described by the ionic two-sublattice model with the formula (Al+3, Y+3)(p)(AlO2-1, O-2, SiO4-4, SiO4-4, SiO20)(Q). The SiO2 solubility in the YAM phase was described using a Compound energy model. Two clatasets of self-consistent model parameters are presented. However, the rather meagre and scattered experimental data imply that the present assessments should be regarded as provisional. Some critical experiments are suggested for this system.

  • 30.
    Mao, Huahai
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Selleby, Malin
    KTH, Superseded Departments, Materials Science and Engineering.
    Sundman, Bo
    KTH, Superseded Departments, Materials Science and Engineering.
    A re-evaluation of the liquid phases in the CaO-Al2O3 and MgO-Al2O3 systems2004In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 28, no 3, p. 307-312Article in journal (Refereed)
    Abstract [en]

    The thermodynamic properties of the liquid phases in the CaO-Al2O3 and MgO-Al2O3 systems are reassessed in order to provide an adequate basis for fitting information on the ternary CaO-Al2O3-SiO2 and MgO-AI(2)O(3)-SiO2 systems, especially the miscibility gap. The modelling of Al2O3 in the liquid phase is modified from the traditional formulae with the liquid phase now described by the ionic two-sublattice model as (Al+3, Ca+2)p(AlO2-1, O-2)(Q) and (Al+3, Mg+2)(P)(AlO2-1, O-2)(Q), respectively.

  • 31.
    Mao, Huahai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sundman, Bo
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Phase equilibria and thermodynamics in the Al(2)O(3)-SiO(2) system: Modeling of mullite and liquid2005In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 88, no 9, p. 2544-2551Article in journal (Refereed)
    Abstract [en]

    The AI(2)O(3)-SiO2 system has been reassessed using a solution model for mullite extending from sillimanite to a hypothetical state of alumina. The property of sillimanite, to be used to describe one of the end-members, was extracted from an analysis of the T-P phase diagram for AI(2)SiO(5) polymorphs. It was possible to represent the information on the range of stability of mullite, including some showing that mullite extends to higher SiO2 contents than represented by the composition of 3:2 mullite. An attempt was made to model the liquid with the ionic two-sublattice model using a new species AIO(2)(-1). The pressure dependence of AI(2)SiO(5) polymorphs was optimized by a new model recently implemented in Thermo-Cale.

  • 32.
    Mao, Huahai
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Sundman, Bo
    KTH, Superseded Departments, Materials Science and Engineering.
    Wang, Z. W.
    Saxena, S. K.
    Volumetric properties and phase relations of silica - thermodynamic assessment2001In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 327, no 1-2, p. 253-262Article in journal (Refereed)
    Abstract [en]

    Taking into account various available experimental data, an improved internally consistent data set for the SiO2 system is obtained by thermodynamic assessment. The volumetric properties for SiO2 polymorphs are reassessed using the CALPHAD method. A two-coefficient expression is used to describe the thermal expansion and bulk modulus. For liquid phase, one equation is achieved in the temperature range of 298-4000 K either for thermal expansion or for bulk modulus. Phase diagrams have been calculated up to 40 GPa. It has been concluded that, in the pressure range lower than 20 GPa, there is no significant difference between the phase diagrams calculated by the Birch-Murnaghan equation of state (EOS) and by Murnaghan EOS.

  • 33.
    Masood, Ansar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Oak, J. J
    Mao, H.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Belova, Lyubov
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Inoue, A.
    Rao, K. V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Distinct Plasticity of Biocompatible Ti-Zr-Cu-Pd-Sn Bulk Metallic GlassManuscript (preprint) (Other academic)
    Abstract [en]

    We have developed Ti-Zr-Cu-Pd-Sn bulk metallic glass without toxic elements which exhibits distinct plasticity (~12.6%) by revealing strain hardening before failure. Specimens performed under compression tests do not show any crystalline phases which usually enhance plasticity by branching or restricting the rapid propagation of shear bands. Along with excellent mechanical properties alloy exhibits appreciably high bulk forming ability, GFA, with large supercooled regime (~56K) and as a consequence cylindrical rods of at least 7mm were fabricated directly by Cu-mold casting. The combination of such mechanical properties and appreciably high bulk forming ability makes it a potential candidate for biomedical applications.   

  • 34.
    Masood, Ansar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Oak, J. J
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Belova, Lyubov
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Rao, K. Venkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Excellent bulk forming ability and high plasticity of Biocompatible Titanium based bulk metallic glassesManuscript (preprint) (Other academic)
    Abstract [en]

    A series of bulk glassy alloys of Ti-Zr-Cu-Pd-Sn composition without toxic elements (Ni, Be, Al) were investigated that revealed excellent bulk forming ability by exhibiting large supercooled regions (ΔTx≥56K), high values of  reduced glass transition temperature (Trg ≥0.56) and the γ parameter (γ ≥ 0.39). As a consequence of large ΔTx≈70K glassy rods of at least 14mm diameter of Ti38.5Zr11.2Cu33.2Pd14.3Sn2.8 (Ti15) alloy were fabricated by direct Cu-mold casting. Uniaxial compressive test performed at room temperature showed high fracture strength (≥2070MPa) and good plasticity (≥5.8%) for all studied alloys. High bulk forming ability along with excellent plasticity (~6.8%) of Ti38.5Zr11.2Cu33.2Pd14.3Sn2.8 (Ti15) alloy as compare to other toxic free titanium based bulk metallic glasses (BMGs) makes it a potential candidate for biomedical application point of view. 

  • 35.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effect of Carbon Content on the Potency of the Intragranular Ferrite Formation2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, no 3, p. 311-319Article in journal (Refereed)
    Abstract [en]

    The effect of the carbon content on the potency of the intragranular ferrite (IGF) formation for each inclusion size is investigated in the present work. The TiN inclusion was detected to be the effective nucleation site for the IGF formation in the Fe-0.2 mass% C alloy and the Fe-0.4 mass% C alloy. It is noted that the potency of the IGF formation for each inclusion size is decreased with the increase of carbon content. Moreover, the critical diameters of the TiN, TiO, and VN inclusions in the steels with different carbon contents are calculated based on the classical nucleation theory. The calculated critical diameter is also found to be decreased with the increase of carbon content. This is in agreement with the experiment results. Finally, the decrease of the potency of IGF formation for each inclusion size is due to a larger amount of pearlite formation in the steel containing a higher carbon content, which is detected by differential scanning calorimetry (DSC) measurements.

  • 36.
    Omori, Toshihiro
    et al.
    KTH.
    Bigdeli, Sedigheh
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    A Generalized Approach Obeying the Third Law of Thermodynamics for the Expression of Lattice Stability and Compound Energy: A Case Study of Unary Aluminum2018In: JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION, ISSN 1547-7037, Vol. 39, no 5, p. 519-531Article in journal (Refereed)
    Abstract [en]

    Recently, Hillert and Selleby proposed a simple method for expression of the lattice stability or Gibbs energy of formation that does not violate the third law of thermodynamics. This method describes the derivation of the Gibbs energy function from high temperatures down to 0 K by interpolation, instead of extrapolation from room temperature to 0 K. In the present work, their original method is discussed in terms of determination of the characteristic parameter values. Keeping the essential interpolation character of their method, a generalized approach is presented for expressing the lattice stability through parameter optimizations. This approach retains the zero point entropy of substances and is in line with the development of the third generation CALPHAD databases. Using the Al unary system as a case study, the lattice stabilities of the hcp and bcc phases are investigated. The respective Einstein temperatures are also evaluated. At high temperatures, the present descriptions reproduce the lattice stabilities suggested by SGTE for the existing second generation of databases, with a reasonable accuracy. More importantly, information from ab initio calculations (total energy at 0 K) is also used for this optimization and the present method results in a physically sounder description of thermodynamic properties at lower temperatures down to 0 K. The present approach provides a simple and flexible way to estimate the lattice stabilities, with potential applicability for the Gibbs energy of formation of stoichiometric compounds and the excess energy of solution phases, in accordance with the third law of thermodynamics.

  • 37.
    Shaw, Cliff S. J.
    et al.
    Univ New Brunswick, Dept Earth Sci, 2 Bailey Dr, Fredericton, NB E3C 1G1, Canada..
    Klausen, Kim B.
    Univ New Brunswick, Dept Earth Sci, 2 Bailey Dr, Fredericton, NB E3C 1G1, Canada..
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Kinetics of dissolution of sapphire in melts in the CaO-Al2O3-SiO2 system2018In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 229, p. 129-146Article in journal (Refereed)
    Abstract [en]

    The dissolution rate of sapphire in melts in the CAS system of varying silica activity, viscosity and degree of alumina saturation has been determined at 1600 degrees C and 1.5 GPa. After an initiation period of up to 1800 s, dissolution is controlled by diffusion of cations through the boundary layer adjacent to the dissolving sapphire. The dissolution rate decreases with increasing silica activity, viscosity and molar Al2O3/CaO. The calculated diffusion matrix for each solvent melt shows that CAS 1 and 9 which have molar Al2O3/CaO of 0.33 and 0.6 and dissolution rate constants of 0.65 x 10(-6) and 0.59 x 10(-6) m/s(0.5) have similar directions and magnitudes of diffusive coupling: DCaO-Al2O3 and DAl2O3-CaO are both negative are approximately equal. The solvent with the fastest dissolution rate: CAS 4, which has a rate constant of 1.5 x 10(-6) m/s(0.5) and Al2O3/CaO of 0.31 has positive DCaO-Al2O3 and negative DAl2O3-CaO and the absolute values vary by a factor of 4. Although many studies show that aluminium is added to the melts via the reaction: Si4+ = Al3+ + 0.5 Ca2+ the compositional profiles show that this reaction is not the only one involved in accommodating the aluminium added during sapphire dissolution. Rather, aluminium is incorporated as both tetrahedrally coordinated Al charge balanced by Ca and as aluminium not charge balanced by Ca (termed Al-xs). This reaction: Al-IV-Ca = Al-xs thorn Ca-NBO where Ca-NBO is a non-bridging oxygen associated with calcium, may involve the formation of aluminium triclusters. The shape of the compositional profiles and oxide-oxide composition paths is controlled by the aluminium addition reaction. When Al-xs exceeds 2%, CaO diffusion becomes increasingly anomalous and since the bond strength of Al-xs correlates with CaO/CaO + Al2O3, the presence of more than 2% Al-xs leads to significantly slower dissolution than when Al-xs is absent or at low concentration. Thus, dissolution is controlled by diffusion of cations through the boundary layer, but this diffusion is itself controlled by the structural modifications required by the addition of new components to the melt. Comparison of quartz dissolution rates in similar melts shows that dissolution is much faster for quartz than for sapphire and that dissolution rates show the same correlation with silica activity and viscosity. We suggest that diffusive fluxes are related to changes in melt structure and the nature of the reaction that incorporates the added component. For the slow eigendirection, SiO2 addition occurs by a single reaction whereas Al2O3 addition requires a more complex two part reaction in which Al is accommodated by charge balance with Ca until Al is in excess of that which can be charge balanced. The Al-xs incorporation reaction, is slower than the Si incorporation reaction which inhibits sapphire dissolution relative to quartz in melts of the same composition.

  • 38. Sheikh, Saad
    et al.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Guo, Sheng
    Predicting solid solubility in CoCrFeNiMx (M=4d transition metal) high-entropy alloys2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 19, article id 194903Article in journal (Refereed)
    Abstract [en]

    CoCrFeMnNi is a prototype fcc-structured high-entropy alloy. Numerous efforts have been paid to strengthen CoCrFeMnNi, by replacing Mn with other elements for an enhancement of the solid solution strengthening. 4d transition metals, including Zr, Nb, and Mo, are of interest for this purpose, since they have much larger atomic radii than that of Mn. However, Nb and Mo are known to have a low solid solubility in fcc-structured CoCrFeNi. Compared to Nb and Mo, Zr has an even larger atomic radius. The solid solubility of Zr in fcc-structured CoCrFeNi was investigated in this work, combining both experimental studies and thermodynamic calculations. In addition, based on previous results and new results obtained here, methods to predict the solid solubility in CoCrFeNiMx (M = Zr, Nb, and Mo) alloys were developed. Particularly, the average d-orbital energy level, Md, was re-evaluated in the present work, for an improved predictability of the solid solubility in fcc-structured high entropy alloys containing 4d transition metals.

  • 39. Tabeshian, A.
    et al.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Arnberg, L.
    Aune, R. E.
    Investigation of glass forming ability in the Zr-rich part of the Zr-Fe-Al ternary system2019In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 125, no 6, article id 065101Article in journal (Refereed)
    Abstract [en]

    In the present study, the CALPHAD (CALculation of PHAse Diagrams) methodology and thermodynamic data were used to calculate the equilibrium phase diagram of the Zr-Fe-Al system. Furthermore, the information for the enthalpy of mixing (ΔH mix ) and the atomic radius of the constituent elements, in terms of the generalized topological instability factor (λ), were combined with the ternary phase diagram to predict compositions with high Glass Forming Ability (GFA). Compositions with a Zr content ranging from 67 to 73 at. % were proposed and later produced by rapid cooling using suction casting. The obtained results revealed that 12 out of the initial 14 compositions were successfully made into glassy structures with a critical diameter ranging from 0.5 to 2.5 mm. The achieved results show good agreement between the predictions made and the experimental results, and the corresponding λ value obtained for the highest GFA was used to identify the optimum area of interest for producing Zr-Fe-Al metallic glasses. It is believed that the proposed computational approach can be used as a guideline to predict glass forming areas/compositions in even other systems.

  • 40.
    Wang, Wei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Northeast Elect Power Univ, China.
    Chen, Hai-Lin
    Thermo Calc Software, Solna, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermo-Calc Software, Solna.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermodynamic constitution of the Al-Cu-Ni system modeled by CALPHAD and ab initio methodology for designing high entropy alloys2019In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 65, p. 346-369Article in journal (Refereed)
    Abstract [en]

    The Al-Cu-Ni system has been thermodynamically assessed over the whole composition and temperature range based on a critical literature review. The L1(2) and B2 phases, in conjunction with their disordered counterparts, are described using partitioning models. Ab initio calculations were performed to support the assessment of these phases. A set of self-consistent thermodynamic parameters for describing the Gibbs energy of individual phases was obtained. The assessment was validated by comparing various calculations such as invariant reaction equilibria, thermochemical properties, isothermal and isoplethal sections with all available experimental data. The Al-Cu-Ni ternary is a vital subsystem of many high entropy alloys (HEAs), which can probably be attributed to the existence of stable ordered and disordered FCC and BCC structures. In near-equiatomic compositions of this ternary system, the phase formation and equilibrium and non-equilibrium solidification curves were calculated using the present thermodynamic description. The phase competitions and their impacts on the design of HEM are discussed, e.g. the relative stability of the disordered FCC and BCC for dual-phase HEAs, and the equilibria between disordered FCC_A1 and ordered B2 phases for ductile high strength HEM.

  • 41. Wang, Z
    et al.
    Griffin, W.L.
    O'Reilly, S.Y.
    Zheng, H.
    Mao, Huahai
    The boundary phase and the melting of CaSiO3 and MgSiO3 perovskites2000In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, Vol. 61, no 11, p. 1815-1820Article in journal (Refereed)
    Abstract [en]

    We have investigated the melting temperatures of MgSiO3 and CaSiO3 perovskites at high pressure conditions, using an empirical melting equation, combined with the assumption of a boundary phase existing at the melting point. This study indicates that both CaSiO3 and MgSiO3 perovskites have a cubic structure near the melting boundary, and that the obtained melting temperatures are in good agreement with experimental measurements (Zerr et al., Geophys. Res. Lett. 24 (1998) 909; J.S. Sweeney, D.L. Heinz, High Pressure-Temperature Research: Properties of Earth and Planetary Materials, in: M.H. Manghnani, T. Yagi (Eds.), AGU, (1998) p. 185]. Additionally, our results reveal that CaSiO3 and MgSiO3 perovskites cannot cause a partial melting at the core-mantle boundary. Our calculation and assumption suggest that the Lindemann law is valid to estimate the melting temperatures of silicates as the silicate phases near the melting boundary are definitely determined and chosen.

  • 42. Wang, Z. W.
    et al.
    Mao, Huahai
    Saxena, S. K.
    The melting of corundum (Al2O3) under high pressure conditions2000In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 299, no 1-2, p. 287-291Article in journal (Refereed)
    Abstract [en]

    We have developed a simple model to address the melting of corundum (Al2O3). For this simple model, a critical volume representative for the melting point was determined, and by employing the relation between thermal pressure and temperature, the melting point of corundum at high pressure conditions can be obtained. This study indicates that a good agreement exists between our calculation, experimental results, and two-phase molecular dynamics simulations for corundum (Al2O3).

  • 43. Xia, S.
    et al.
    Lousada, Claudio M.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermo-Calc Software AB, Solna, Sweden.
    Maier, A. C.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Y.
    Zhang, Y.
    Nonlinear oxidation behavior in pure Ni and Ni-containing entropic alloys2018In: Frontiers in Materials, ISSN 2296-8016, Vol. 5, article id 53Article in journal (Refereed)
    Abstract [en]

    We performed a combined experimental and theoretical investigation of the oxidation behavior of pure Ni and of the following multi-component Ni-containing alloys with nearly equiatomic compositions: FeNi, CoFeNi, CoCrFeNi, and CoCrFeMnNi. The materials were exposed to air at ambient pressure and at a temperature of 800°C for 150 min, their weight-gain due to oxidation was continuously monitored and the products of oxidation were subsequently characterized by XRD. The most common oxides formed have spinel or halite structure and the materials resistance to oxidation increases as: FeNi &lt; CoFeNi &lt; Ni &lt; CoCrFeMnNi &lt; CoCrFeNi. We found further that the oxidation-resistance of the materials does not correlate linearly with the number of elements present, instead the type of elements impacts significantly the materials susceptibility to oxidative damage. Cr is the element that imparted higher resistance to oxidation while Mn and Fe worsened the materials performance. In order to better understand the mechanisms of oxidation we employed thermodynamic equilibrium calculations and predicted the phase stability of oxides of the elements that are present in the materials, in different ranges of temperature, composition and oxygen activity. Additionally, we determined the phase compositions for the thermodynamically stable oxides at 800°C. The results from the thermodynamic modeling are in good agreement with the experimental finds. The alloys with low resistance to oxidation such as CoFeNi and FeNi, form the Fe 3 O 4 spinel phase which tends to dominate the phase diagram for these materials. The presence of Cr increases the resistance to atomic rearrangement due to slow diffusion in the complex structure of Cr containing spinel phases. This causes the extremely high resistance to oxidation of the CoCrFeNi alloy. The presence of Mn in CoCrFeNi stabilizes the Mn 3 O 4 spinel, which reduces the oxidation-resistance of the alloys due to the high mobility of Mn.

  • 44.
    Xia, Songqin
    et al.
    Univ Sci & Technol Beijing, State Key Lab Adv Met & Mat, Beijing, Peoples R China.;Peking Univ, State Key Lab Nucl Phys & Technol, Beijing, Peoples R China.;KTH Royal Inst Technol, Dept Mat Sci & Engn, Stockholm, Sweden..
    Lousada, Claudio M.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermocalc Software AB, Solna, Sweden..
    Maier, Annika C.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Yugang
    Peking Univ, State Key Lab Nucl Phys & Technol, Beijing, Peoples R China..
    Zhang, Yong
    Univ Sci & Technol Beijing, State Key Lab Adv Met & Mat, Beijing, Peoples R China..
    Nonlinear Oxidation Behavior in Pure Ni and Ni-Containing Entropic Alloys (vol 5, 53, 2018)2018In: FRONTIERS IN MATERIALS, ISSN 2296-8016, Vol. 5, article id 73Article in journal (Refereed)
  • 45. Xia, Songqin
    et al.
    Lousada, Claudio M.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Mao, Huahai
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Maier, Annika Carolin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Korzhavyi, Pavel A.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Y.
    Zhang, Y.
    Erratum: Nonlinear oxidation behavior in pure Ni and Ni-containing entropic alloys (Front. Mater., (2018) 5, 53, 10.3389/fmats.2018.00053)2018In: Frontiers in Materials, ISSN 2296-8016, Vol. 5, article id 73Article in journal (Refereed)
    Abstract [en]

    In the original article, there was an error. An explanation should be inserted at the beginning of the section Thermodynamic Calculations, Paragraph 1, line 1: In this as well as the following paragraphs the authors refer to phases such as halite, spinel, corundum etc. It thereby solely referred to the structure type and not the respective mineral. In the original article, there was an error. The word "sfinancial" should be corrected to "financial" in the Acknowledgements section, Paragraph 1: The Carl Tryggers Stiftelse för Vetenskaplig Forskning is gratefully acknowledged for financial support. The authors apologize for these errors and state that they do not change the scientific conclusions of the article in any way. The original article has been updated.

  • 46.
    Yang, Yang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Chen, Hai-Lin
    Thermo-Calc Software AB, Norra Stationsgatan 93, 113 64 Stockholm, Sweden..
    An assessment of the Ti-V-O systemArticle in journal (Other academic)
  • 47.
    Yang, Yang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    An assessment of the Ca-V-O system2017In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, p. 29-40Article in journal (Refereed)
    Abstract [en]

    The Ca-V-O system is studied with an emphasis on the following oxide sub-systems: CaO-V2O5, CaO-V2O3, V2O5-CaV2O5 and CaO-V2O5-VO2. The aim of the present assessment is to obtain a thermodynamic description of the Ca-V-O system. The compound energy formalism was used to describe the liquid by applying the ionic two-sublattice model and the β-bronze phase CaxV2O5 (0.17≤x≤0.33) using a three-sublattice model. Phase equilibria and thermodynamic properties were critically evaluated using the CALPHAD approach and a consistent set of thermodynamic model parameters was obtained. Satisfactory agreement between calculated and experimental values is achieved.

  • 48.
    Yang, Yang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermo-Calc Software AB, Sweden.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermo-Calc Software AB, Sweden.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermo-Calc Software AB, Sweden.
    An assessment of the Ti-V-O system2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 722, p. 365-374Article in journal (Refereed)
    Abstract [en]

    The Ti-V-O system has been assessed using the CALPHAD method based on recent assessments of its binary systems. The present work focuses on the following oxide sub-systems: V2O3-TiO2, VO2-TiO2, V2O5-TiO2 and V2O3-Ti2O3-TiO2. The liquid phase was described by the ionic liquid model while the solid solution oxide phases were modeled using a two-sublattice model within the framework of the compound energy formalism. The available experimental data were critically evaluated and a consistent set of thermodynamic model parameters was obtained. Satisfactory agreement between calculated and experimental information especially of the stability, solubility and phase relations of various oxide phases is achieved. Reliable predictions of oxygen solubility in Ti-V alloys can be made using the present thermodynamic descriptions.

  • 49.
    Yang, Yang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics. Thermo-Calc Software AB, Norra Stationsgatan 93, Stockholm, Sweden.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Thermodynamic assessment of the V-O system2015In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 51, p. 144-160Article in journal (Refereed)
    Abstract [en]

    The V-O system was thermodynamically assessed using the CALPHAD method. The available experimental data on thermodynamic and thermochemical properties as well as phase diagram information were critically examined and a self-consistent set of thermodynamic parameters was obtained. In total 20 phases were included in this binary system. Five among them were treated as solid solution phases within the framework of the compound energy formalism. The halite phase was modeled as (V,V+2,V+3,Va)<inf>1</inf>(O-2,Va)<inf>1</inf> covering the solubility of both V and O. Thermodynamic descriptions of two different models for the corundum phase are presented, one of which is more complex to correctly take the defect mechanisms into account. The liquid phase was described by the ionic two-sublattice model with the formula (V+2)<inf>P</inf>(O-2,Va-Q, VO<inf>1.5</inf>,VO<inf>2</inf>, VO<inf>2.5</inf>)<inf>Q</inf>. The stoichiometric Magnéli phases V<inf>n</inf>O<inf>2n-1</inf> (n is an integer between 4 and 8) were modeled as (V+3)<inf>2</inf>(V+4)<inf>n-2</inf>(O-2)<inf>2n-1</inf>. Using the present thermodynamic description reliable experimental phase diagram, thermodynamic and thermochemical data were well reproduced.

  • 50.
    Yin, Jun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mathematical Modelling of the Initial Mold Filling with Utilization of an Angled Runner2019In: Metals, ISSN 2075-4701, Vol. 9, no 6Article in journal (Refereed)
    Abstract [en]

    The flow pattern plays a crucial role in the uphill teeming process. The non-metallic inclusion generation due to interaction with the mold flux is believed to be influenced by the flow pattern. In this study, a three-dimensional mathematical model of the filling of a gating system for 10, 20, and 30 degrees angled runners was used to predict the fluid flow characteristics. Moreover, a mathematical model with a horizontal runner was applied as a reference. The predictions indicate that the angled-runner-design decreases the hump height during the initial filling stage, which results in less entrapment of mold flux into the mold. Nevertheless, increasing the angle of runner can result in a lower hump height, while the 30 degree angled runner gives a much more stable increase of the hump height during the initial filling stage. Besides CFD calculations, some thermodynamic calculations are taken into account for the chemical reactions between liquid steel and gas. The results show that the bubble shrinks due to the fact that N and O are dissolved into steel. The present findings strongly suggest that changing the horizontal runner to an angled runner would be an effective means of reducing flow unevenness during the initial filling of ingots, if the added steel losses are deemed acceptable.

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