清华大学：《材料科学基础》课程教学资源（PPT课件讲稿）Chapter 5. 3 Origin of Concept for Dislocation

35.3 Origin of Concept for Dislocate ion Discrepancies between theory and practice in Deformation 1. Morphology of the surface in deformation 2. The great difference between theoretical and actual strength of single crystals(t. >>T)

§5.3 Origin of Concept for Dislocation Discrepancies between theory and practice in Deformation. 1. Morphology of the surface in deformation. 2. The great difference between theoretical and actual strength of single crystals ( ). c   

S P 2=6

=b x  ’ b a   ’ S.P. x

Assuming t=Tm sin b x:displacement Of atoms 2元 For small x T=m b Gr=G( G b 2丌 2丌 zm~10 10 MPa IMPa

x: displacement of atoms For small x: ( ) a x = Gr = G ( ) 2 m a G b   = ～ 2 G 10 10 MPa 1MPa C 3 4  .m ～ −  ～ Assuming  = m sin b 2x  = m b 2x

35. 4 What's Dislocation ◆|.By| oca slip According to the relative orientation of the slip direction and the line of demarcation between slipped and unslipped zones, the follows types of dislocation can be formed 1.edge dislocation 2 screw dislocation 3. mixed dislocation

§5.4 What’s Dislocation ◆ Ⅰ.By local slip According to the relative orientation of the slip direction and the line of demarcation between slipped and unslipped zones, the follows types of dislocation can be formed. 1. edge dislocation 2. screw dislocation 3. mixed dislocation

1. Edge dislocation Slip plane Dislocation line

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •  W 1. Edge dislocation

A ↓ ⊥) (T)

（⊥） （ ） ⊥

2. Screw dislocation 8 3『6生5 A

2. Screw dislocation

DISLOCATION LINE

3. Mixed dislocation b Edge Screw

3. Mixed dislocation