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Simulation of diffusional processes in alloys: techniques and applications
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis concerns computer simulation of diffusional processes in alloys. The main focus is on the development of simulation techniques for diffusion in single-phase domains, but also diffusion controlled phase-transformations and interfacial processes are discussed.

Different one-dimensional simulation techniques for studying the Kirkendall effect are developed and analyzed. Comparisons with experimentally observed marker migration show good agreement for small shifts and comparisons with observed Kirkendall porosity show reasonable agreement under the assumption that a certain supersaturation is needed before the vacancies coalesce into pores.

A convenient approach in simulations of kinetics is to use thermodynamic software, e.g. Thermo-Calc, to calculate thermodynamic quantities, e.g. chemical potentials, required in the simulation. The main drawback with such an approach is that it will generate a large amount of additional computational work. To overcome this problem a method that decreases the amount of computational work has been developed. The new method is based on artificial neural networks (ANN). By training the ANN to estimate thermodynamic quantities a significant increase in computational speed was obtained.

By calculating the dissipation of available driving force due to diffusion inside migrating interfaces an approach for including the effect of solute drag in computer simulations of grain growth and phase transformations has been developed. The new method is based on an effective interfacial mobility and simulations of grain growth have been performed in binary and ternary systems using experimentally assessed model parameters.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , vii, 39 p.
Keyword [en]
Diffusion, Kirkendall effect, Phase transformations, Random walk, Solute drag, Interfacial mobility
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-399ISBN: 91-7178-116-1 (print)OAI: oai:DiVA.org:kth-399DiVA: diva2:10280
Public defence
2005-09-09, Sal B2, Brinellvägen 23, Stockholm, 12:00
Opponent
Supervisors
Note
QC 20100930Available from: 2005-08-23 Created: 2005-08-23 Last updated: 2010-09-30Bibliographically approved
List of papers
1. High-speed thermodynamic calculations for kinetic simulations
Open this publication in new window or tab >>High-speed thermodynamic calculations for kinetic simulations
2004 (English)In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Computational materials science, Vol. 29, no 2, 187-194 p.Article in journal (Refereed) Published
Abstract [en]

Simulation of phase transformations may be divided into two parts: the simulation of kinetics and the calculation of thermodynamic quantities. A number of softwares for thermodynamic calculations are available and it is thus convenient to use such software to obtain an accurate description of thermodynamic properties and couple them to a software simulating the kinetics. A major problem then is that the computational work to evaluate the thermodynamic quantities is often too heavy unless very simplified thermodynamic models are used. That problem may be solved by calculating the thermodynamic quantities in selected points and time steps only and apply an artificial neural network to obtain the values in all other points. This approach has successfully been applied to diffusion in alloys and has enabled us to incorporate thermodynamic data from the Thermo-Calc software package into simulations of diffusion in a very efficient way.

Keyword
artificial neural networks, CALPHAD, computational thermodynamics, diffusion, kinetics, random walk
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5779 (URN)10.1016/j.commatsci.2003.09.001 (DOI)000188089700007 ()2-s2.0-0346093924 (Scopus ID)
Note
QC 20100930Available from: 2005-08-23 Created: 2005-08-23 Last updated: 2017-12-14Bibliographically approved
2. Prediction of Kirkendall shift and porosity in binary and ternary diffusion couples
Open this publication in new window or tab >>Prediction of Kirkendall shift and porosity in binary and ternary diffusion couples
2004 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 52, no 15, 4695-4703 p.Article in journal (Refereed) Published
Abstract [en]

Computer simulations are applied to simulate the Kirkendall shift and porosity in binary and ternary alloys. Three different computational methods, based on different assumptions, are used together with assessed thermodynamic and kinetic data. The simulation results show good agreement compared with experimental data.

Keyword
Diffusion, Kinetics, Kirkendall effect, Modelling, Simulation, Concentration (process), Crystal lattices, Diffusion, Heat treatment, Porosity, Reaction kinetics, Ternary systems, Thermodynamics
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-12690 (URN)10.1016/j.actamat.2004.06.039 (DOI)000223793900028 ()2-s2.0-4043050123 (Scopus ID)
Note
QC 20100506 QC 20110916Available from: 2010-05-06 Created: 2010-05-06 Last updated: 2017-12-12Bibliographically approved
3. Diffusion process simulations - an overview of different approaches
Open this publication in new window or tab >>Diffusion process simulations - an overview of different approaches
2004 (English)In: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum, ISSN 1012-0386, E-ISSN 1662-9507, Vol. 233, 97-113 p.Article in journal (Refereed) Published
Abstract [en]

Some different approaches to diffusion process simulations are briefly presented. Their varying areas of applicability are discussed. Example simulations using the phase-field method, the DICTRA software, and random-walk based approaches are presented.

Keyword
diffusion, Kirkendall effect, phase transformations, simulation
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5781 (URN)10.4028/www.scientific.net/DDF.233-234.97 (DOI)000228123900009 ()2-s2.0-17144384408 (Scopus ID)
Note
QC 20100930Available from: 2005-08-23 Created: 2005-08-23 Last updated: 2017-12-14Bibliographically approved
4. Simulation of diffusion by direct solution in the lattice-fixed frame of reference
Open this publication in new window or tab >>Simulation of diffusion by direct solution in the lattice-fixed frame of reference
2006 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 37A, no 6, 1785-1789 p.Article in journal (Refereed) Published
Abstract [en]

A new simulation method for bulk diffusion that automatically takes the Kirkendall effect into account is presented. Example simulations are presented and compared with experimental data and DICTRA simulations.

Keyword
thermo-calc; alloys, system, dictra
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5782 (URN)10.1007/s11661-006-0120-0 (DOI)000238020000009 ()2-s2.0-33745230123 (Scopus ID)
Conference
Hillert Symposium on Thermodynamics and Kinetics of Migrating Interfaces in Steels and Other Complex Alloys Royal Inst Technol, Stockholm, SWEDEN, DEC 02-03, 2004
Note
QC 20100930. Conference: Hillert Symposium on Thermodynamics and Kinetics of Migrating Interfaces in Steels and Other Complex Alloys. Royal Inst Technol, Stockholm, SWEDEN. DEC 02-03, 2004Available from: 2005-08-23 Created: 2005-08-23 Last updated: 2017-12-14Bibliographically approved
5. An effective mobility approach to solute drag in computer simulations of migrating grain boundaries
Open this publication in new window or tab >>An effective mobility approach to solute drag in computer simulations of migrating grain boundaries
2008 (English)In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 44, no 2, 265-273 p.Article in journal (Refereed) Published
Abstract [en]

An approach for taking solute drag into account in simulations of grain boundary migration in multicomponent systems in two or three dimensions has been developed. The new method is based on an effective mobility which is a function of the thermodynamic properties in the bulk and the grain boundary and the total driving force. Examples from phase-field simulations in Fe-Ni and Ni-Cr-Fe are presented.

Keyword
Diffusion, Grain growth, Modelling, Segregation, Simulations
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5783 (URN)10.1016/j.commatsci.2008.03.030 (DOI)000261731700009 ()2-s2.0-55949133756 (Scopus ID)
Note
Uppdaterad från manuskript till artikel: 20100930. QC 20100930Available from: 2005-08-23 Created: 2005-08-23 Last updated: 2017-12-14Bibliographically approved
6. Computer simulations of solute drag in grain boundary migration and phase transformations
Open this publication in new window or tab >>Computer simulations of solute drag in grain boundary migration and phase transformations
2005 (English)In: Solid-Solid Phase Transformations in Inorganic Material 2005, Vol 2 / [ed] Howe, JM; Laughlin, DE; Lee, JK; Dahmen, U; Soffa, WA, 2005, 817-822 p.Conference paper, Published paper (Refereed)
Abstract [en]

The effect of alloying elements on migrating interfaces, so-called solute drag, has been studied for many years and different theoretical treatments have been presented. In this work the approach based on the dissipation of Gibbs energy due to diffusion inside the interface, originally introduced by Hillert and Sundman, has been applied and coupled to simulations of grain growth using the phase-field method. In the phase-field simulations an effective mobility, which takes the effect of solute-drag into account, has been formulated and implemented into a phase-field software. The approach is not restricted only to curvature driven grain growth, also recrystallization can be taken into account. In addition, the austenite to ferrite transformation has been studied using a recent coupling between the DICTRA software and the dissipation of Gibbs energy approach.

Keyword
grain growth, modelling, simulation, phase-field
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5784 (URN)000238838100089 ()2-s2.0-33645238076 (Scopus ID)
Conference
International Conference on Solid-Solid Phase Transformations in Inorganic Materials (PTM 2005) Location: Phoenix, AZ Date: MAY 29-JUN 03, 2005
Note
QC 20111007Available from: 2005-08-23 Created: 2005-08-23 Last updated: 2011-10-17Bibliographically approved
7. Grain growth in Fe, Fe-Cu and Fe-Mn - simulations and experiments
Open this publication in new window or tab >>Grain growth in Fe, Fe-Cu and Fe-Mn - simulations and experiments
(English)Manuscript (Other academic)
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5785 (URN)
Note
QC 20100930Available from: 2005-08-23 Created: 2005-08-23 Last updated: 2010-09-30Bibliographically approved

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