Tài liệu bề mặt kim loại cấu trúc nano

Contents
Introduction 1
1 Peculiarities of the Metallic Surface 7
1.1 Surface Energy and Surface Stress 7
1.2 Crystal Structure of a Surface 11
1.3 Surface Defects 14
1.4 Distribution of Electrons near the Surface 18
1.4.1 Model of Free Electrons in Solids 20
1.4.2 Semi-Infinite Chain 24
1.4.3 Infinite Surface Barrier 26
1.4.4 The Jellium Model 27
1.5 Summary 30
2 Some Experimental Techniques 33
2.1 Diffraction Methods 33
2.1.1 The Low-Energy Electron Diffraction Method 33
2.1.2 The Reflection High-Energy Electron Diffraction Method 40
2.1.3 The X-ray Measurement of Residual Stresses 40
2.1.3.1 Foundation of the Method 41
2.1.3.2 Experimental Installation and Precise Technique 44
2.1.4 Calculation of Microscopic Stresses 47
2.2 Distribution of Residual Stresses in Depth 47
2.3 The ElectronicWork Function 48
2.3.1 Experimental Installation 50
2.3.2 Measurement Procedure 52
2.4 Indentation of Surface. Contact Electrical Resistance 53
2.5 Materials under Investigation 55
2.6 Summary 56
VI Contents
3 Experimental Data on the Work Function of Strained Surfaces 59
3.1 Effect of Elastic Strain 59
3.2 Effect of Plastic Strain 61
3.2.1 Physical Mechanism 65
3.3 Influence of Adsorption and Desorption 67
3.4 Summary 71
4 Modeling the Electronic Work Function 73
4.1 Model of the Elastic Strained Single Crystal 73
4.2 Taking into Account the Relaxation and Discontinuity of the Ionic
Charge 76
4.3 Model for Neutral Orbital Electronegativity 78
4.3.1 Concept of the Model 78
4.3.2 Effect of Nanodefects Formed on the Surface 81
4.4 Summary 83
5 Contact Interaction of Metallic Surfaces 87
5.1 Mechanical Indentation of the Surface Layers 87
5.2 Influence of Indentation and Surface Roughness on theWork
Function 93
5.3 Effect of Friction andWear on Energetic Relief 95
5.4 Summary 100
6 Prediction of Fatigue Location 103
6.1 Forecast Possibilities of theWork Function. Experimental
Results 104
6.1.1 Aluminum and Titanium-Based Alloys 104
6.1.2 Superalloys 107
6.2 Dislocation Density in Fatigue-Tested Metals 109
6.3 Summary 112
7 Computer Simulation of Parameter Evolutions during Fatigue 115
7.1 Parameters of the Physical Model 115
7.2 Equations 115
7.2.1 Threshold Stress and Dislocation Density 116
7.2.2 Dislocation Velocity 116
7.2.3 Density of Surface Steps 117
7.2.4 Change in the ElectronicWork Function 117
7.3 System of Differential Equations 118
7.4 Results of the Simulation: Changes in the Parameters 118
7.5 Summary 120
Contents VII
8 Stressed Surfaces in the Gas-Turbine Engine Components 123
8.1 Residual Stresses in the Surface of Blades and Disks and Fatigue
Strength 123
8.1.1 Turbine and Compressor Blades 124
8.1.2 Grooves of Disks 126
8.2 Compressor Blades of Titanium-Based Alloys 128
8.2.1 Residual Stresses and Subgrain Size 130
8.2.2 Effect of Surface Treatment on Fatigue Life 133
8.2.3 Distribution of Chemical Elements 137
8.3 Summary 140
9 Nanostructuring and Strengthening of Metallic Surfaces. Fatigue
Behavior 143
9.1 Surface Profile and Distribution of Residual Stresses with
Depth 144
9.2 Fatigue Strength of the Strained Metallic Surface 150
9.3 Relaxation of the Residual Stresses under Cyclic Loading 154
9.4 Microstructure and Microstructural Stability 161
9.5 Empirical and Semi-Empirical Models of Fatigue Behavior 165
9.5.1 Fatigue-Crack Propagation in Linear Elastic Fracture
Mechanics 166
9.5.2 Crack Propagation in a Model Crystal 171
9.6 Prediction of Fatigue Strength 173
9.7 Summary 178
10 The Physical Mechanism of Fatigue 181
10.1 Crack Initiation 181
10.2 Periods of Fatigue-Crack Propagation 192
10.3 Crack Growth 195
10.4 Evolution of Fatigue Failure 205
10.5 S – N curves 213
10.6 Influence of Gas Adsorption 215
10.7 Summary 216
11 Improvement in Fatigue Performance 219
11.1 Restoring Intermediate Heat Treatment 219
11.2 Effect of the Current Pulse on Fatigue 220
11.3 The Combined Treatment of Blades 223
11.4 Structural Elements of Strengthening 226
11.5 Summary 231
VIII Contents
12 Supplement I 233
12.1 List of Symbols 233
12.1.1 Roman Symbols 233
12.1.2 Greek Symbols 235
13 Supplement II 237
13.1 Growth of a Fatigue Crack. Description by a System of Differential
Equations 237
13.1.1 Parameters to be Studied 237
13.1.2 Results 238
References 243
Index 247