High Temperature Strain Of Metals And Alloys - Physical Fundamentals

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.

Professor Valim Levitin is the Head of an internationally renowned Research Group at the National Technical University in Ukraine. His work focusses on problems of atom vibrations in solids, work function, physical bases of creep and fatigue and X-ray and TEM studies of the fundamentals of materials strength.

Introduction.

1 Macroscopic Characteristics of Strain of Metallic Materials at High Temperatures.

2 In situ X-ray Investigation Technique.

2.1 Experimental Installation.

2.2 Measurement Procedure.

2.3 Measurements of Structural Parameters.

2.4 Diffraction Electron Microscopy.

2.5 Amplitude of Atomic Vibrations.

2.6 Materials under Investigation.

2.7 Summary.

3 Structural Parameters in High-Temperature Deformed Metals.

3.1 Evolution of Structural Parameters.

3.2 Dislocation Structure.

3.3 Distances between Dislocations in Sub-boundaries.

3.4 Sub-boundaries as Dislocation Sources and Obstacles.

3.5 Dislocations inside Subgrains.

3.6 Vacancy Loops and Helicoids.

3.7 Total Combination of Structural Peculiarities of High-temperature Deformation.

3.8 Summary.

4 Physical Mechanism of Strain at High Temperatures.

4.1 Physical Model and Theory.

4.2 Velocity of Dislocations.

4.3 Dislocation Density.

4.4 Rate of the Steady-State Creep.

4.5 Effect of Alloying: Relationship between Creep Rate and Mean-Square Atomic Amplitudes.

4.6 Formation of Jogs.

4.7 Significance of the Stacking Faults Energy.

4.8 Stability of Dislocation Sub-boundaries.

4.9 Scope of the Theory.

4.10 Summary.

5 Simulation of the Parameters Evolution.

5.1 Parameters of the Physical Model.

5.2 Equations.

5.2.1 Strain Rate.

5.2.2 Change in the Dislocation Density.

5.2.3 The Dislocation Slip Velocity.

5.2.4 The Dislocation Climb Velocity.

5.2.5 The Dislocation Spacing in Sub-boundaries.

5.2.6 Variation of the Subgrain Size.

5.2.7 System of Differential Equations.

5.3 Results of Simulation.

5.4 Density of Dislocations during Stationary Creep.

5.5 Summary.

6 High-temperature Deformation of Superalloys.

6.1 γ Phase in Superalloys.

6.2 Changes in the Matrix of Alloys during Strain.

6.3 Interaction of Dislocations and Particles.

6.4 Creep Rate. Length of Dislocation Segments.

6.5 Mechanism of Strain and the Creep Rate Equation.

6.6 Composition of the γ Phase and Atomic Vibrations.

6.7 Influence of the Particle Size and Concentration.

6.8 The Prediction of Properties.

6.9 Summary.

7 Single Crystals of Superalloys.

7.1 Effect of Orientation on Properties.

7.2 Deformation at Lower Temperatures.

7.3 Deformation at Higher Temperatures.

7.4 On the Composition of Superalloys.

7.5 Rafting.

7.6 Effect of Composition and Temperature on γ/γ Misfit.

7.7 Other Creep Equations.

7.8 Summary.

8 Deformation of Some Refractory Metals.

8.1 The Creep Behavior.

8.2 Alloys of Refractory Metals.

8.3 Summary.

Supplements.

Supplement 1: On Dislocations in the Crystal Lattice.

Supplement 2: On Screw Components in Sub-boundary Dislocation Networks.

Supplement 3: Composition of Superalloys.

References.

Acknowledgements.

Index.