In the 1950s the direct observation of dislocations became possible, stimulat ing the interest of many research workers in the dynamics of dislocations. This led to major contributions to the understanding of the plasticity of various crys talline materials. During this time the study of metals and alloys of fcc and hcp structures developed remarkably. In particular, the discovery of the so-called in ertial effect caused by the electron and phonon frictional forces greatly influenced the quantitative understanding of the strength of these metallic materials. Statis tical studies of dislocations moving through random arrays of point obstacles played an important role in the above advances. These topics are described in Chaps. 2-4. Metals and alloys with bcc structure have large Peierls forces compared to those with fcc structure. The reasons for the delay in studying substances with bcc structure were mostly difficulties connected with the purification techniques and with microscopic studies of the dislocation core. In the 1970s, these difficulties were largely overcome by developments in experimental techniques and computer physics. Studies of dislocations in ionic and covalent bonding materials with large Peierls forces provided infonnation about the core structures of dislocations and their electronic interactions with charged particles. These are the main subjects in Chaps. 5-7.

Contenu

Dislocations and Their Fundamental Properties.- 1.1 Geometry of a Dislocation.- 1.2 Stress Field and Energy of Dislocations.- 1.3 Force on a Dislocation.- 1.4 String Model of a Dislocation.- 1.5 Obstacles to Dislocation Motion.- 2. Motion of Dislocations in Soft Metals.- 2.1 General Characteristics.- 2.2 Intrinsic and Extrinsic Barriers for the Motion of Dislocations.- 2.3 Dislocation Velocity.- 2.3.1 General.- 2.3.2 Characteristics of Dislocation Motion in fcc and hcp Metals.- 2.3.3 The Steady-State Velocity and Number of Moving Dislocations.- 2.4 Frictional Forces due to Conduction Electrons and Phonons.- 2.5 Theoretical Studies of the Frictional Forces.- 2.5.1 Frictional Force due to Conduction Electrons.- 2.5.2 Frictional Force due to Phonons.- 3. Dislocation Motion in the Field of a Random Distribution of Point Obstacles: Solution Hardening.- 3.1 Solution Hardening.- 3.1.1 Experimental.- 3.1.2 Theoretical.- 3.2 Comparison of Theories of Solution Hardening with Computer Simulation.- 3.3 Effect of a Random Distribution of Point Obstacles on ?c.- 3.4 Appendix: Elastic Interaction Between a Dislocation and a Solute Atom.- 4. Dislocation Dynamics and Strength of Crystalline Materials.- 4.1 The Loss of Strength of Metals and Alloys in the Superconducting State.- 4.1.1 Temperature Dependence.- 4.1.2 Impurity Dependence.- 4.1.3 Strain-Rate Dependence.- 4.1.4 Anomalous Strain-Rate Dependence.- 4.1.5 Strain Dependence.- 4.2 Loss of Strength in the Normal State of Solid Solutions at Low Temperatures.- 4.3 Theory of Inertial Effects.- 4.3.1 Inertial Theory.- 4.3.2 Excitation of Quasiparticles by Moving Dislocations and Anomalous Strain-Rate Sensitivity of Bs.- 4.4 Quantitative Treatment of the Strength of Metals and Alloys of fcc Structure.- 4.4.1 Unzipping Effect.- 4.4.2 Effects of Inertia on the Activation Process.- 4.4.3 Quantitative Analysis of ??ns.- 4.4.4 Effect of Inertia on the Activation Volume.- 5. Dislocation Motion Controlled by the Peieris Mechanism.- 5.1 Introduction.- 5.2 Dislocation Glide by the Peieris Mechanism.- 5.2.1 Smooth Kink Model.- 5.2.2 Dislocation Velocity in the Smooth Kink Model.- 5.2.3 Abrupt Kink Model.- 6. Dislocations in bcc Metals and Their Motion.- 6.1 Dislocations in bcc Metals and Their Peierls Potential.- 6.2 Computer Experiments.- 6.2.1 Crystal Geometry and Peierls Stress.- 6.2.2 Core Structure of a Screw Dislocation.- 6.2.3 Behavior Under Stress.- 6.3 Plasticity of bcc Metals.- 6.3.1 Yielding of bcc Metals.- 6.3.2 Plasticity of bcc Metal Single Crystals.- 7. Dislocation Motion in Semiconducting Crystals.- 7.1 Introduction.- 7.2 Structure of Dislocations in Semiconducting Crystals.- 7.2.1 Atomic Structure.- 7.2.2 Electronic Structure of the Dislocation Core.- 7.3 Mobility of Dislocations in Semiconducting Crystals.- 7.3.1 Experimental Facts.- 7.3.2 The Mechanism Controlling the Mobility.- 7.4 Effect of Electronic Excitation on the Dislocation Mobility.- 7.5 Photoplastic Effect in II-VI Compounds.- 7.5.1 Plasticity and Dislocation Motion in II-VI Compounds.- 7.5.2 Photoplastic Effect.- 8. High-Temperature Deformation of Metals and Alloys.- 8.1 Deformation Mechanism Map.- 8.1.1 Dislocation Glide.- 8.1.2 Diffusional Creep.- 8.1.3 Power Law Creep.- 8.1.4 Harper-Dorn Creep.- 8.1.5 Effect of Internal Structure.- 8.1.6 Others.- 8.2 Deformation due to Dislocation Motion.- 8.2.1 Thermal and Athermal Processes.- 8.2.2 Viscous Motion and High-Speed Motion of Dislocations.- 8.3 Identification of Deformation Mechanism at High Temperatures.- 8.3.1 Temperature Change Technique.- 8.3.2 Strain Rate Change Technique.- 8.3.3 Stress Dip Technique.- 8.3.4 Stress Change Technique.- 8.3.5 Fundamental Problems in Internal Stress Measurement.- 8.3.6 Techniques to Determine Whether the Effective Stress Is Appreciable or Negligible.- 9. High-Temperature Deformation Mechanism in Metals and Alloys.- 9.1 High-Temperature Deformation Mechanism in Pure Metals.- 9.1.1 Jog-Drag Theory.- 9.1.2 Theory of Recovery Control.- 9.1.3 Effect of Inhomogeneity in the Dislocation Structure.- 9.1.4 Experimental Values of h and r.- 9.2 High-Temperature Deformation Mechanism in Alloys.- 9.2.1 High-Temperature Deformation Behavior of Solution-Hardened Alloys.- 9.2.2 Drift Flow of Solute Atoms Relative to a Moving Dislocation.- 9.2.3 Resistance to Dislocation Motion due to Solute Atmosphere.- 9.2.4 Interpretation of High-Temperature Deformation Behavior of Alloys.- 10. High-Temperature Deformation Mechanism in Composite Materials.- 10.1 Types of Composite Materials.- 10.2 High-Temperature Deformation Mechanism in Dispersion-Strengthened Materials.- 10.2.1 Climb Model.- 10.2.2 Attractive Interaction.- 10.3 High-Temperature Deformation Mechanism in Fiber- and Lamella-Reinforced Materials.- References.