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Experimental Investigation and Computer Simulation of Diffusion in Fe˗Mo and Fe˗Mn˗Mo Alloys with Different Optimization Methods
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
Shanghai Univ, Sch Mat Sci & Engn, Shanghai 200444, Peoples R China..
Shanghai Univ, Sch Mat Sci & Engn, Shanghai 200444, Peoples R China..
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2017 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48, p. 536-550Article in journal (Refereed) Published
Abstract [en]

In order to simulate the diffusional phase transformations involving the fcc and bcc phases for microalloyed steels, the diffusion mobilities for fcc and bcc Fe˗Mo and Fe˗Mn˗Mo alloys were experimentally investigated and critically assessed. The diffusion-couple technique was employed to extract the interdiffusion coefficients in Fe˗Mo and Fe˗Mn˗Mo alloys with the Sauer-Freise and Whittle-Green methods. Based on the present experimental interdiffsivities, the mobility parameters for the fcc and bcc phases in the Fe˗Mo and Fe˗Mn˗Mo systems were optimized using the traditional method. Simultaneously, a direct method was developed and utilized to directly fit mobilities to the diffusion profiles rather than the diffusivities in the present work. The satisfactory description of the diffusion behavior in the Fe˗Mo and Fe˗Mn˗Mo systems has confirmed the reliability of the direct method. Particularly, the two sets of diffusion mobilities obtained with both methods could simulate the diffusion phenomenon between the fcc and bcc phases in the Fe˗Mo and Fe˗Mn˗Mo systems successfully.

Place, publisher, year, edition, pages
2017. Vol. 48, p. 536-550
Keywords [en]
Diffusion mobility, Direct method, Diffusion couple, Fe˗Mo, Fe˗Mn˗Mo, Fcc and bcc
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-228398DOI: 10.1007/s11661-016-3822-yISI: 000391492200049Scopus ID: 2-s2.0-84991758453OAI: oai:DiVA.org:kth-228398DiVA, id: diva2:1209698
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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Ågren, John

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