لایب سان

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 VI Contents 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 VII 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

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