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Thermodynamic modeling of the Al-C-Mn system supported by ab initio calculations
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
Shanghai Univ, Sch Mat Sci & Engn, Shanghai 200444, Peoples R China..
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.ORCID iD: 0000-0002-8493-9802
Shanghai Univ, Sch Mat Sci & Engn, Shanghai 200444, Peoples R China..
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2018 (English)In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, p. 222-230Article in journal (Refereed) Published
Abstract [en]

A CALPHAD-type thermodynamic assessment of the Al-C-Mn system was carried out in the present work. Special attention was paid to the ternary κ-phase with the aid of ab initio calculations. The enthalpies of formation at 0 K of all end-members of the κ phase were derived from the ab initio calculations and utilized in the present optimization. The κ phase was modeled as an ordered form of the fcc structure for the substitutional sub-lattices, employing the following formula within the framework of compound energy formalism: (Al,Mn)0.25(Al,Mn)0.25(Al,Mn)0.25(Al,Mn)0.25(C,Va)0.25. With the present optimized model parameters, the wide homogeneity range of the κ phase was reproduced satisfactorily. Comparison between the predicted and measured phase equilibria as well as the ab initio calculation results validates the present optimized model parameters.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA , 2018. p. 222-230
Keywords [en]
Al-C-Mn, kappa phase, partitioning model, ab initio, CALPHAD
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-228395DOI: 10.1016/j.calphad.2018.01.007ISI: 000428000100024Scopus ID: 2-s2.0-85043301506OAI: oai:DiVA.org:kth-228395DiVA, id: diva2:1209694
Note

QC 20180524

Available from: 2018-05-23 Created: 2018-05-23 Last updated: 2018-05-24Bibliographically approved
In thesis
1. Thermodynamic and kinetic investigation of systems related to lightweight steels
Open this publication in new window or tab >>Thermodynamic and kinetic investigation of systems related to lightweight steels
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lightweight steels have attracted considerable interest for automobile applications due to the weight reduction without loss of high strength and with retained excellent plasticity. In austenitic Fe-Mn-Al-C steels, the nano-precipitation of the κ-carbide within the austenitic matrix significantly contributes to the increase in yield strength. In the present work, the precipitation strengthening simulation has been carried out within the framework of the ICME approach. Thermodynamic assessments of the quaternary Fe-Mn-Al-C system as well as its sub-ternary systems were performed with the CALPHAD method. All available information on phase equilibria and thermochemical properties were critically evaluated and used to optimize the thermodynamic model parameters. By means of the partitioning model, the κ-carbide was described using a five-sublattice model (four substitutional and one interstitial sublattice), which can reflect the ordering between metallic elements and reproduce the wide homogeneity range of the κ-carbide. Based on the present thermodynamic description, a thermodynamic database for lightweight steels was created. Using the database, the phase equilibria evolution in lightweight steels can be satisfactorily predicted, as well as the partition of alloying elements. In order to accelerate the development of a kinetic database for multicomponent systems, a high-throughput optimization method was adopted to optimize the diffusion mobilities. This method may largely reduce the necessary diffusion-couple experiments in multicomponent systems. Based on the developed thermodynamic and kinetic databases for lightweight steels, the precipitation of the κ-carbide was simulated using TC-PRISMA. The volume fraction and particle size were reasonably reproduced. Finally, the precipitation strengthening contribution to the yield strength was predicted. The calculation results show that the anti-phase boundary effect is predominant in the precipitation strengthening. Overall, the relationship between the composition, processing parameters, microstructure and mechanical properties are established in the thesis.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2018. p. 74
Series
TRITA-ITM-AVL ; 2018:34
Keywords
Fe-Mn-Al-C, CALPHAD, MGI, ICME, Precipitation strengthening, Lightweight steels.
National Category
Materials Engineering
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-228401 (URN)978-91-7729-840-3 (ISBN)
Public defence
2018-09-21, rum 4301, Brinellvägen 8, Stockholm, 10:00 (English)
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Note

QC 20180524

Available from: 2018-05-24 Created: 2018-05-23 Last updated: 2018-05-24Bibliographically approved

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Mao, HuahaiSelleby, MalinÅgren, John

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