Solid-solid phase transformation kinetics [Elektronische Ressource] / vorgelegt von Rico Bauer

Bauer

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• Publié par: universitat_stuttgart
• Publié le: 01 janvier 2010
• Nombre de lectures: 10
• Poids de l'ouvrage: 7 Mo

Extrait

Max-Planck-Institut für Metallforschung
Stuttgart
Solid-Solid Phase Transformation Kinetics
Rico Bauer
Dissertation
an der
Universität Stuttgart
Bericht Nr. 230
November 2010
















Solid-Solid Phase Transformation Kinetics
Von der Fakultät Chemie der Universität Stuttgart
zur Erlangung der Würde eines Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigte Abhandlung
vorgelegt von
Rico Bauer
aus Jena
Hauptberichter: Prof. Dr. Ir. E. J. Mittemeijer
Mitberichter: Prof. Dr. J. Bill
Prüfungsvorsitzender: Prof. Dr. Th. Schleid

Tag der Einreichung: 18.08.2010
Tag der mündlichen Prüfung: 23.11.2010
MAX-PLANCK-INSTITUT FÜR METALLFORSCHUNG STUTTGART
INSTITUT FÜR MATERIALWISSENSCHAFT DER UNIVERSITÄT STUTTGART
Stuttgart 2010






Contents
1 Introduction ................................................................................................................................ 7
1.1 Modular Phase Transformation Model ......................................................................... 10
1.2 Focus of this Thesis ....................................................................................................... 14
1.3 Methodology ................................................................................................................. 15
1.3.1 Differential Scanning Calorimetry ................................................................... 15
1.3.2 (High-Resolution) Transmission Electron Microscopy .................................... 17
1.4 Investigated Systems ..................................................................................................... 18
1.4.1 Co ..................................................................................................................... 18
1.4.2 AuCo ................................................................................................................ 18
1.4.3 CuCo ................................................................................................................. 20
1.5 Outline of this Thesis .................................................................................................... 21
2 Natural Formation of bcc Co; The Initial Stage of Co Precipitation in
Supersaturated Au Co Alloy ................................................................................................. 25 90 10
2.1 Introduction ................................................................................................................... 26
2.2 Experimental ................................................................................................................. 26
2.3 Results ........................................................................................................................... 27
2.4 Discussion ..................................................................................................................... 33
2.5 Summary ....................................................................................................................... 36
3 Precipitation of Co from Supersaturated Au Co : Microstructure and Kinetics .................... 39 90 10
3.1 Introduction ................................................................................................................... 40
3.2 Theoretical Considerations ............................................................................................ 41
3.2.1 Thermodynamics .............................................................................................. 41
3.2.1.1 Transformation Enthalpy ................................................................... 41
3.2.1.2 Gibbs Energy Barrier for Nucleation ................................................. 42
3.2.2 Transformation Kinetics; The Modular Model ................................................ 44
3.2.2.1 Extended Transformed Fraction ......................................................... 44
3.2.2.2 Impingement Modes .......................................................................... 45
3.2.2.3 Determination of Kinetic Parameters ................................................. 46
3.3 Experimental ................................................................................................................. 47
3.3.1 Alloy Production .............................................................................................. 47
3.3.2 Differential Scanning Calorimetry ................................................................... 47
3.3.3 X-Ray Diffraction............................................................................................. 48
3.3.4 Hardness Measurement .................................................................................... 48
3.3.5 Electron Microscopy – SEM, TEM and HRTEM ............................................ 49
3.4 Results and Evaluation .................................................................................................. 49
3.4.1 Differential Scanning Calorimetry ................................................................... 49
3.4.2 X-Ray Diffractometry ...................................................................................... 53
4 Content
3.4.3 Hardness Measurement .................................................................................... 55
3.4.4 Electron Microscopy – SEM, TEM and HRTEM ............................................ 56
3.4.4.1 As-quenched ....................................................................................... 56
3.4.4.2 Isochronal Annealing ......................................................................... 56
3.4.4.3 Isothermal Annealing ......................................................................... 61
3.4.5 Kinetic Analysis ............................................................................................... 62
3.4.5.1 Model Fitting Procedure .................................................................... 62
3.4.5.2 Fitting the Data ................................................................................... 65
3.5 Discussion ..................................................................................................................... 71
3.5.1 Microstructural Evolution ................................................................................ 71
3.5.2 Kinetics ............................................................................................................. 74
3.6 Conclusions ................................................................................................................... 76
4 The Kinetics of the Precipitation of Co from Supersaturated Cu-Co Alloy ............................ 81
4.1 Introduction ................................................................................................................... 82
4.2 Theoretical Background of Transformation Kinetics .................................................... 83
4.3 Experimental ................................................................................................................. 87
4.4 Results and Evaluation .................................................................................................. 88
4.4.1 Differential Scanning Calorimetry ................................................................... 88
4.4.2 (HR)TEM ......................................................................................................... 89
4.4.3 Analysis of Transformation Kinetics ................................................................ 91
4.5 Discussion ..................................................................................................................... 97
4.6 Conclusions ................................................................................................................. 100
5 Kinetics of the Allotropic hcp-fcc Phase Transformation in Cobalt ...................................... 103
5.1 Introduction ................................................................................................................. 104
5.2 Theoretical Background of Transformation Kinetics .................................................. 105
5.2.1 The hcp↔fcc Transformation Mechanism ..................................................... 106
5.2.2 Nucleation....................................................................................................... 108
5.2.3 Interface-Controlled Growth .......................................................................... 112
5.2.4 Extended Fraction, Transformed Fraction and Impingement ......................... 113
5.3 Experimental ............................................................................................................... 113
5.3.1 Alloy Production ............................................................................................ 113
5.3.2 Differential Scanning Calorimetry ................................................................. 114
5.3.3 X-Ray Diffraction ........................................................................................... 115
5.3.4 Light Microscopy ........................................................................................... 115
5.4 Results and Evaluation ................