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Tabeshian, A., Mao, H., Arnberg, L. & Aune, R. E. (2019). Investigation of glass forming ability in the Zr-rich part of the Zr-Fe-Al ternary system. Journal of Applied Physics, 125(6), Article ID 065101.
Open this publication in new window or tab >>Investigation of glass forming ability in the Zr-rich part of the Zr-Fe-Al ternary system
2019 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 125, no 6, article id 065101Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-244326 (URN)10.1063/1.5066554 (DOI)000458877500026 ()2-s2.0-85061368608 (Scopus ID)
Note

QC 20190220

Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2019-03-18Bibliographically approved
Omori, T., Bigdeli, S. & Mao, H. (2018). A Generalized Approach Obeying the Third Law of Thermodynamics for the Expression of Lattice Stability and Compound Energy: A Case Study of Unary Aluminum. JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION, 39(5), 519-531
Open this publication in new window or tab >>A Generalized Approach Obeying the Third Law of Thermodynamics for the Expression of Lattice Stability and Compound Energy: A Case Study of Unary Aluminum
2018 (English)In: JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION, ISSN 1547-7037, Vol. 39, no 5, p. 519-531Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
aluminum, excess energy, Gibbs energy of formation, lattice stability, thermodynamic database, third generation of CALPHAD databases
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-236002 (URN)10.1007/s11669-018-0641-4 (DOI)000444765000007 ()2-s2.0-85048360999 (Scopus ID)
Funder
VINNOVA, 2012-02892
Note

QC 20181016

Available from: 2018-10-16 Created: 2018-10-16 Last updated: 2018-12-03Bibliographically approved
Chen, H.-L., Mao, H. & Chen, Q. (2018). Database development and Calphad calculations for high entropy alloys: Challenges, strategies, and tips. Materials Chemistry and Physics, 210, 279-290
Open this publication in new window or tab >>Database development and Calphad calculations for high entropy alloys: Challenges, strategies, and tips
2018 (English)In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 210, p. 279-290Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
High entropy alloys, Calphad, Thermodynamic database, Thermodynamic calculation
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-226744 (URN)10.1016/j.matchemphys.2017.07.082 (DOI)000429762200037 ()2-s2.0-85028308669 (Scopus ID)
Note

QC 20180503

Available from: 2018-05-03 Created: 2018-05-03 Last updated: 2018-05-03Bibliographically approved
Abu-Odeh, A., Galvan, E., Kirk, T., Mao, H., Chen, Q., Mason, P., . . . Arróyave, R. (2018). Efficient exploration of the High Entropy Alloy composition-phase space. Acta Materialia, 152, 41-57
Open this publication in new window or tab >>Efficient exploration of the High Entropy Alloy composition-phase space
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2018 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 152, p. 41-57Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Acta Materialia Inc, 2018
Keywords
Alloy design, CALPHAD, Constraint satisfaction problem, High-Entropy Alloys
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-227544 (URN)10.1016/j.actamat.2018.04.012 (DOI)000436650600005 ()2-s2.0-85045696607 (Scopus ID)
Note

QC 20180509

Available from: 2018-05-09 Created: 2018-05-09 Last updated: 2018-07-17Bibliographically approved
Holmström, E., Lizarraga, R., Linder, D., Salmasi, A., Wang, W., Kaplan, B., . . . Vitos, L. (2018). High entropy alloys: Substituting for cobalt in cutting edge technology. Applied Materials Today, 12, 322-329
Open this publication in new window or tab >>High entropy alloys: Substituting for cobalt in cutting edge technology
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2018 (English)In: Applied Materials Today, ISSN 2352-9407, Vol. 12, p. 322-329Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
High entropy alloys, Cemented carbides, Cobalt binder, Alternative binders, Density functional theory, Calphad
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-235109 (URN)10.1016/j.apmt.2018.07.001 (DOI)000443213700028 ()2-s2.0-85049613452 (Scopus ID)
Funder
VINNOVA, 2016-00805Swedish Research CouncilSwedish Foundation for Strategic Research The Swedish Foundation for International Cooperation in Research and Higher Education (STINT)Carl Tryggers foundation
Note

QC 20180919

Available from: 2018-09-19 Created: 2018-09-19 Last updated: 2018-11-13Bibliographically approved
Shaw, C. S. J., Klausen, K. B. & Mao, H. (2018). Kinetics of dissolution of sapphire in melts in the CaO-Al2O3-SiO2 system. Geochimica et Cosmochimica Acta, 229, 129-146
Open this publication in new window or tab >>Kinetics of dissolution of sapphire in melts in the CaO-Al2O3-SiO2 system
2018 (English)In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 229, p. 129-146Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Sapphire dissolution, CaO-Al2O3-SiO2 system, Dissolution kinetics, Silicate melt structure
National Category
Geochemistry Geophysics
Identifiers
urn:nbn:se:kth:diva-226738 (URN)10.1016/j.gca.2018.03.011 (DOI)000429426600008 ()
Note

QC 20180504

Available from: 2018-05-04 Created: 2018-05-04 Last updated: 2018-05-04Bibliographically approved
Xia, S., Lousada, C. M., Mao, H., Maier, A. C., Korzhavyi, P. ., Sandström, R., . . . Zhang, Y. (2018). Nonlinear Oxidation Behavior in Pure Ni and Ni-Containing Entropic Alloys (vol 5, 53, 2018). FRONTIERS IN MATERIALS, 5, Article ID 73.
Open this publication in new window or tab >>Nonlinear Oxidation Behavior in Pure Ni and Ni-Containing Entropic Alloys (vol 5, 53, 2018)
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2018 (English)In: FRONTIERS IN MATERIALS, ISSN 2296-8016, Vol. 5, article id 73Article in journal (Refereed) Published
Place, publisher, year, edition, pages
FRONTIERS MEDIA SA, 2018
Keywords
single-phase multicomponent alloys, oxidation, thermodynamic calculations, high-entropy alloys, nonlinear behavior
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-239990 (URN)10.3389/fmats.2018.00073 (DOI)000451624300001 ()
Note

QC 20181211

Available from: 2018-12-11 Created: 2018-12-11 Last updated: 2018-12-11Bibliographically approved
Chen, K., Chen, X., Wang, Z., Mao, H. & Sandström, R. (2018). Optimization of deformation properties in as-cast copper by microstructural engineering. Part I. microstructure. Journal of Alloys and Compounds, 763, 592-605
Open this publication in new window or tab >>Optimization of deformation properties in as-cast copper by microstructural engineering. Part I. microstructure
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2018 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 763, p. 592-605Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Casting, Copper, Microstructure design, Grain refinement, Iron-rich nanoparticle
National Category
Ceramics
Identifiers
urn:nbn:se:kth:diva-234567 (URN)10.1016/j.jallcom.2018.05.297 (DOI)000442484300068 ()2-s2.0-85048149452 (Scopus ID)
Note

QC 20180919

Available from: 2018-09-19 Created: 2018-09-19 Last updated: 2018-09-19Bibliographically approved
Lu, Y., Gao, X., Dong, Y., Wang, T., Chen, H.-L., Mao, H., . . . Guo, S. (2018). Preparing bulk ultrafine-microstructure high-entropy alloys via direct solidification. Nanoscale, 10(4), 1912-1919
Open this publication in new window or tab >>Preparing bulk ultrafine-microstructure high-entropy alloys via direct solidification
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2018 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, no 4, p. 1912-1919Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-222414 (URN)10.1039/c7nr07281c (DOI)000423355300041 ()29318249 (PubMedID)2-s2.0-85041175969 (Scopus ID)
Note

QC 20180228

Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2018-05-24Bibliographically approved
Gunasekara, S. N., Mao, H., Bigdeli, S., Chiu, J. & Martin, V. (2018). Thermodynamic assessment of binary erythritol-xylitol phase diagram for phase change materials design. Calphad, 60, 29-36
Open this publication in new window or tab >>Thermodynamic assessment of binary erythritol-xylitol phase diagram for phase change materials design
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2018 (English)In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 60, p. 29-36Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
CALPHAD, Erythritol-xylitol phase diagram, Gibbs free energy minimization, Phase change material (PCM), Thermal energy storage (TES), Thermodynamic optimization
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-219591 (URN)10.1016/j.calphad.2017.11.005 (DOI)000428000100004 ()2-s2.0-85035018780 (Scopus ID)
Note

QC 20171208

Available from: 2017-12-08 Created: 2017-12-08 Last updated: 2018-04-16Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8493-9802

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