清华大学：《材料科学基础》课程教学资源（PPT课件讲稿）Chapter 5.6 Dislocation in Motion

85.6 Dis location in Mot ion 从 It stress stress A H Unit step K. Chen

§5.6 Dislocation in Motion

◆|. Edge dislocate i on 1. Slip(glide) Dislocation motion vs atom movement Direction:l⊥ Plane:l×b(1×w Dislocation motion vs, crystal movement. z→ crystal movement→v( dislocation motion

◆ Ⅰ.Edge dislocation 1. Slip (glide) ◆ Dislocation motion vs. atom movement. ◆ Direction: ◆ Plane: ◆ Dislocation motion vs. crystal movement. l v   ⊥ l b (// l v)       v    crystal movement  (dislocation motion)

I xv directs to the part of the crystal which moves along b τ→ crystal movement→v Q33 Ship plane Q Stip plure Direction of dis/ocation movement

directs to the part of the crystal which moves along . l v    b  v    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

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

2 Climb D Dislocation moves along n induced by diffusion Plane I×v a Dislocation motion VS crystal movement

2. Climb ① Dislocation moves along induced by diffusion. ② ③ Plane ④ Dislocation motion vs. crystal movement. ns  v l   ⊥ l v    ⊥ ⊥ b  v 

positive climb晶体合拢 negative climb晶体分开

positive climb 晶体合拢 negative climb 晶体分开

I. screw dislocation ① only slip ②2p⊥l 3pane:l× E B (4 dislocation motion VS. crystal movement Macroscopic deformation =-6 Ad- area over which dislocation swept A5-area of slip plane or climb plane

◆ Ⅱ.Screw dislocation ① only slip. ② ③ plane: ④ dislocation motion vs. crystal movement. Macroscopic deformation = Ad —— area over which dislocation swept. As —— area of slip plane or climb plane. v l   ⊥ l v    b A A s d b      v 

Examp le: gIven. a dislocation loop ABCD on z plane with Burgers Vector b, b=a[0101, and the applied stress(i) around the loop determine. the possible movement of each segment of the loop

◆ Ⅲ.Example: 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 ABCD b  b = a[010]   ij

∠ A D B

A B C D x y z 0  zx  yx  x  zy  y  xy yz  xz  z b 