skja_19 Imperfections in Crystals 材料科学基础（英文课件）.pptVIP

材料科学基础Fundamental of Materials §5.6 Dislocation in Motion Ⅰ.Edge dislocation Slip (glide) Dislocation motion vs. atom movement. Direction: Plane: Dislocation motion vs. crystal movement. Climb Dislocation moves along induced by diffusion. Plane Dislocation motion vs. crystal movement. Ⅱ.Screw dislocation only slip. plane: dislocation motion vs. crystal movement. Macroscopic deformation = Ad —— area over which dislocation swept. As —— area of slip plane or climb plane. Ⅲ.Example: §5.7 Summary —— Properties of Dislocation Line imperfection. It must be a continuous line running through the crystal or a closed loop. Its character can be described by and . The physical meaning and the conservation of . Rule governing the relation among . Dislocation density . ① Definition: ② , , , whisker Examples and Discussions Exercise * * Prof: Tian Min Bo Tel: E-mail: tmb@mail.tsinghua.edu.cn Department of Material Science and Engineering Tsinghua University. Beijing 100084 Lesson nineteen crystal movement (dislocation motion) directs to the part of the crystal which moves along . crystal movement If the dislocation runs through the crystal from one side to the other, the relative displacement of the two parts of the crystal (on both sides of the moving plane) is b. ? ? positive climb 晶体合拢 negative climb 晶体分开 given: a dislocation loop on z plane with Burgers Vector , , and the applied stress ( ) around the loop. determine: the possible movement of each segment of the loop ＝NO. of dislocation emergence x z y