tailieunhanh - Kinetics of Materials - R. Balluff_ S. Allen_ W. Carter (Wiley_ 2005) Episode 7

Tham khảo tài liệu 'kinetics of materials - r. balluff_ s. allen_ w. carter (wiley_ 2005) episode 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 11 MOTION OF DISLOCATIONS The motion of dislocations by glide and climb is fundamental to many important kinetic processes in materials. Gliding dislocations are responsible for plastic deformation of crystalline materials at relatively low temperatures where any dislocation climb is negligible. They also play important roles in the motion of glissile interfaces during twinning and diffusionless martensitic phase transformations. Both gliding and climbing dislocations cause much of the deformation that occurs at higher temperatures where self-diffusion rates become significant and significant climb is then possible. Climbing dislocations act as sources and sinks for point defects. This chapter establishes some of the basic kinetic features of both dislocation glide and climb. GLIDE AND CLIMB The general motion of a dislocation can always be broken down into two components glide motion and climb motion. Glide is movement of the dislocation along its glide slip plane which is defined as the plane that contains the dislocation line and its Burgers vector. Climb is motion normal to the glide plane. Glide motion is a conservative process in the sense that there is no need to deliver or remove atoms at the dislocation core during its motion. In contrast the delivery or removal of atoms at the core is necessary for climb. This is illustrated for the simple case of the glide and climb of an edge dislocation in Fig. . The glide along X in Fig. and b is accomplished by the local conservative shuffling of atoms at the disloca- Kinetics of Materials. By Robert w. Balluffi Samuel M. Allen and w. Craig Carter. 253 Copyright @ 2005 John Wiley Sons Inc. 254 CHAPTER 11 MOTION OF DISLOCATIONS Figure Glide and climb of edge dislocation in primitive cubic crystal b 600 c 001 1 . a and b Glide from left to right c - f Downward climb along y. In d the lighter-shaded substitutional atom shown adjacent to the dislocation core in c has joined the extra half .

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