List of Symbols and Abbreviations .............................. IX
1 Introduction ................................................. 1
2 The Al-Ti-Cr System .......................................... 3
2.1 Binary Systems .......................................... 3
2.1.1 The Al-Cr System ................................. 3
2.1.2 The Al—Ti System ................................. 5
2.1.3 The Cr-Ti System ................................. 7
2.2 Phases in the Ternary Al-Ti-Cr System ................... 9
2.3 Isothermal Sections .................................... 10
2.4 Vertical Sections ...................................... 12
2.5 Liquidus and Solidus Projections ....................... 13
2.6 Assessments, Thermodynamic Data and Modelling .......... 14
2.6.1 Experimental Thermodynamic Data of Phases
stable in the Al-Ti-Cr System ................... 14
2.6.2 Thermodynamic Modelling of the Al-Ti-Cr
System .......................................... 14
2.7 Research Objectives .................................... 17
3 Experimental Procedures ..................................... 19
3.1 Alloy Preparation ...................................... 19
3.2 Heat Treatment Procedures .............................. 20
3.3 Thermal Analysis ....................................... 23
3.3.1 Calibration of Differential Scanning
Calorimeters .................................... 24
3.3.2 Heat Capacity Measurements ...................... 31
3.3.3 Enthalpy Increment .............................. 41
3.4 Scanning Electron Microscopy ........................... 43
3.4.1 Energy-Dispersive X-ray Spectroscopy ............ 43
3.4.2 Electron Backscatter Diffraction ................ 44
3.5 Electron Probe Microanalysis ........................... 45
3.6 X-ray Diffraction - The Rietveld Method ................ 50
4 Results and Discussion ...................................... 55
4.1 Isothermal Section at 1200°C ........................... 55
4.1.1 Phase Equilibria with the r Phase ............... 56
4.1.2 Ternary Extension of the C14 Laves Phase ........ 62
4.1.3 Construction of the Isothermal Section at
1200°C .......................................... 69
4.2 Liquidus and Solidus Projection ........................ 71
4.2.1 Determination of the Primary Crystallized
Phases .......................................... 71
4.2.2 Investigation of the Solidus Surface ............ 78
4.2.3 Construction of the Melting Diagram ............. 86
4.3 Isopleth at 33 at.%Ti .................................. 93
4.4 Thermodynamic Data .................................... 100
4.4.1 The Invariant Reaction γ-TiAl + β  τ + C14 ... 100
5 Conclusion ................................................. 123
Appendix ...................................................... 127
A Rietveld Refinement ..................................... 129
В Differential Thermal Analysis ........................... 137
С Supplementary Material .................................. 147
References .................................................... 162
|
