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Wang, W., Hou, Z., Lizarrága, R., Tian, Y., Babu, P., Holmström, E., . . . Larsson, H. (2019). An experimental and theoretical study of duplex fcc plus hcp cobalt based entropic alloys. Acta Materialia, 176, 11-18
Open this publication in new window or tab >>An experimental and theoretical study of duplex fcc plus hcp cobalt based entropic alloys
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2019 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 176, p. 11-18Article in journal (Refereed) Published
Abstract [en]

Martensitically formed duplex fcc + hcp Co-based entropic alloys have been investigated both experimentally and theoretically. Theoretical predictions are in good agreement with experimental observations. A fair correlation is found between calculated driving forces for a partitionless fcc -> hcp transformation and experimentally obtained phase fractions.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Co-Base alloys, Martensitic phase transformation, Computational thermodynamics, CALPHAD, DFT
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-259436 (URN)10.1016/j.actamat.2019.06.041 (DOI)000482247800002 ()2-s2.0-85068362090 (Scopus ID)
Note

QC 20190924

Available from: 2019-09-24 Created: 2019-09-24 Last updated: 2019-09-24Bibliographically approved
Wang, W., Hou, Z., Lizarrága, R., Tian, Y., Babu, P., Holmström, E., . . . Larsson, H. (2019). An experimental and theoretical study of duplex fcc+hcp cobalt based entropic alloys. Acta Materialia, 176, 11-18
Open this publication in new window or tab >>An experimental and theoretical study of duplex fcc+hcp cobalt based entropic alloys
Show others...
2019 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 176, p. 11-18Article in journal (Refereed) Published
Abstract [en]

Martensitically formed duplex fcc + hcp Co-based entropic alloys have been investigated both experimentally and theoretically. Theoretical predictions are in good agreement with experimental observations. A fair correlation is found between calculated driving forces for a partitionless fcc→hcp transformation and experimentally obtained phase fractions.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-258027 (URN)10.1016/j.actamat.2019.06.041 (DOI)2-s2.0-85068362090 (Scopus ID)
Note

QC 20190917

Available from: 2019-09-09 Created: 2019-09-09 Last updated: 2019-09-17Bibliographically approved
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
Yin, J., Ersson, M., Mao, H. & Jönsson, P. G. (2019). Mathematical Modelling of the Initial Mold Filling with Utilization of an Angled Runner. Metals, 9(6)
Open this publication in new window or tab >>Mathematical Modelling of the Initial Mold Filling with Utilization of an Angled Runner
2019 (English)In: Metals, ISSN 2075-4701, Vol. 9, no 6Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
CFD, bubble, uphill teeming, ingot casting, mathematical modelling, gating system, thermodynamic calculations
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-255577 (URN)10.3390/met9060693 (DOI)000475356500077 ()2-s2.0-85070457970 (Scopus ID)
Note

QC 20190802

Available from: 2019-08-02 Created: 2019-08-02 Last updated: 2019-10-04Bibliographically 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
Xia, S., Lousada, C. M., Mao, H., Maier, A. C., Korzhavyi, P. ., Sandström, R., . . . Zhang, Y. (2018). Erratum: Nonlinear oxidation behavior in pure Ni and Ni-containing entropic alloys (Front. Mater., (2018) 5, 53, 10.3389/fmats.2018.00053). Frontiers in Materials, 5, Article ID 73.
Open this publication in new window or tab >>Erratum: Nonlinear oxidation behavior in pure Ni and Ni-containing entropic alloys (Front. Mater., (2018) 5, 53, 10.3389/fmats.2018.00053)
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2018 (English)In: Frontiers in Materials, ISSN 2296-8016, Vol. 5, article id 73Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2018
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-252249 (URN)10.1177/0956797615602271 (DOI)2-s2.0-85062450216 (Scopus ID)
Note

QC20190612

Available from: 2019-06-12 Created: 2019-06-12 Last updated: 2019-06-12Bibliographically 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
Dilner, D., Kjellqvist, L., Mao, H. & Selleby, M. (2018). Improving Steel and Steelmaking—an Ionic Liquid Database for Alloy Process Design. Integrating Materials and Manufacturing Innovation, 7, 195-201
Open this publication in new window or tab >>Improving Steel and Steelmaking—an Ionic Liquid Database for Alloy Process Design
2018 (English)In: Integrating Materials and Manufacturing Innovation, ISSN 2193-9764, Vol. 7, p. 195-201Article in journal (Refereed) Published
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.

Keywords
CALPHAD; Ionic 2-sublattice liquid model; Steelmaking; Inclusions; Sulphide; Oxide
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-249227 (URN)10.1007/s40192-018-0121-z (DOI)000454133700003 ()
Note

QC 20190617

Available from: 2019-04-11 Created: 2019-04-11 Last updated: 2019-08-27Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8493-9802

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