Creep and fatigue are the most prevalent causes of rupture in superalloys, which are important materials for industrial usage, e.g. in engines and turbine blades in aerospace or in energy producing industries. As temperature increases, atom mobility becomes appreciable, affecting a number of metal and alloy properties. It is thus vital to find new characterization methods that allow an understanding of the fundamental physics of creep in these materials as well as in pure metals.
Here, the author shows how new in situ X-ray investigations and transmission electron microscope studies lead to novel explanations of high-temperature deformation and creep in pure metals, solid solutions and superalloys. This unique approach is the first to find unequivocal and quantitative expressions for the macroscopic deformation rate by means of three groups of parameters: substructural characteristics, physical material constants and external conditions.
Creep strength of the studied up-to-date single crystal superalloys is greatly increased over conventional polycrystalline superalloys.
From the contents:
- Macroscopic characteristics of strain at high temperatures
- Experimental equipment and technique of in situ X-ray investigations
- Experimental data and structural parameters in deformed metals
- Subboundaries as dislocation sources and obstacles
- The physical mechanism of creep and the quantitative structural model
- Simulation of the parameters evolution
- System of differential equations
- High-temperature deformation of industrial superalloys
- Single crystals of superalloys
- Effect of composition, orientation and temperature on properties
- Creep of some refractory metals
For materials scientists, solid state physicists, solid state chemists, researchers and practitioners from industry sectors including metallurgical, mechanical, chemical and structural engineers.
Table of Contents:
Introduction 1
1 Macroscopic Characteristics of Strain of Metallic Materials at High Temperatures 5
2 In situ X-ray Investigation Technique 13
2.1 Experimental Installation 13
2.2 Measurement Procedure 15
2.3 Measurements of Structural Parameters 17
2.4 Diffraction Electron Microscopy 20
2.5 Amplitude of Atomic Vibrations 21
2.6 Materials under Investigation 23
2.7 Summary 24
3 Structural Parameters in High-Temperature Deformed Metals 25
3.1 Evolution of Structural Parameters 25
3.2 Dislocation Structure 30
3.3 Distances between Dislocations in Sub-boundaries 34
3.4 Sub-boundaries as Dislocation Sources and Obstacles 34
3.5 Dislocations inside Subgrains 35
3.6 Vacancy Loops and Helicoids 39
3.7 Total Combination of Structural Peculiarities of High-temperature Deformation 40
3.8 Summary 41
4 Physical Mechanism of Strain at High Temperatures 43
4.1 Physical Model and Theory 43
4.2 Velocity of Dislocations 45
4.3 Dislocation Density 49
4.4 Rate of the Steady-State Creep 51
4.5 Effect of Alloying: Relationship between Creep Rate and Mean-Square Atomic Amplitudes 54
4.6 Formation of Jogs 55
4.7 Significance of the Stacking Faults Energy 57
4.8 Stability of Dislocation Sub-boundaries 58
4.9 Scope of the Theory 62
4.10 Summary 64
5 Simulation of the Parameters Evolution 67
5.1 Parameters of the Physical Model 67
5.2 Equations 68
5.2.1 Strain Rate 68
5.2.2 Change in the Dislocation Density 68
5.2.3 The Dislocation Slip Velocity 69
5.2.4 The Dislocation Climb Velocity 69
5.2.5 The Dislocation Spacing in Sub-boundaries 70
5.2.6 Variation of the Subgrain Size 71
5.2.7 System of Differential Equations 71
5.3 Results of Simulation 71
5.4 Density of Dislocations during Stationary Creep 77
5.5 Summary 80
6 High-temperature Deformation of Superalloys 83
6.1 γ Phase in Superalloys 83
6.2 Changes in the Matrix of Alloys during Strain 88
6.3 Interaction of Dislocations and Particles 89
6.4 Creep Rate. Length of Dislocation Segments 95
6.5 Mechanism of Strain and the Creep Rate Equation 96
6.6 Composition of the γ Phase and Atomic Vibrations 102
6.7 Influence of the Particle Size and Concentration 104
6.8 The Prediction of Properties 106
6.9 Summary 109
7 Single Crystals of Superalloys 111
7.1 Effect of Orientation on Properties 111
7.2 Deformation at Lower Temperatures 116
7.3 Deformation at Higher Temperatures 124
7.4 On the Composition of Superalloys 129
7.5 Rafting 130
7.6 Effect of Composition and Temperature on γ/γ Misfit 136
7.7 Other Creep Equations 137
7.8 Summary 141
8 Deformation of Some Refractory Metals 143
8.1 The Creep Behavior 143
8.2 Alloys of Refractory Metals 149
8.3 Summary 155
Supplements 157
Supplement 1: On Dislocations in the Crystal Lattice 157
Supplement 2: On Screw Components in Sub-boundary Dislocation Networks 161
Supplement 3: Composition of Superalloys 163
References 164
Acknowledgements 168
Index 169
