清华大学：《材料科学基础》课程教学资源（PPT课件讲稿）Chapter 5. 18 Thompson's tetrahedron

35. 18 Thompson's tetrahedron D B 110] (11)(d) (I1 Ir(a) <I0 C A(=0),B(0-),C(0 D(000

§5.18 Thompson’s tetrahedron ), (000) 2 1 2 1 ), (0 2 1 0 2 1 0), ( 2 1 2 1 A( B C D

85.19 Reaction between Dis locat i on I Condition 1. Geometrical condition ∑b=∑b 2. Energy condition ∑b2≥∑b2

§5.19 Reaction between Dislocation ◆ Ⅰ.Condition 1. Geometrical condition 2. Energy condition  =  j j i i b b   2 2    j j i bi b  

Example 1.(FCC) b=AB=-[101 2[101→>[211+121 B 2 ∑ 262=V6 [12] a X 2 cO C ∑b2>∑b2

◆ Ⅱ.Example 1. (FCC) [ 110 ] [ 211 ] [ 1 2 1 ] 61 61 21 → + 2 2 2 2 2 2 2 2 2 31 ) 2 66 ( 21 42 ) 22 (     =  = = = = i j j j i i b b b a a b a a a    [ 110 ] 21 b = AB =  B B C [11 2 ]

AB A A AB (6) A A A方 )

2. Lomer-Cottrell sessile dislocation B A [Il2] [112] A B

2. Lomer-Cottrell sessile dislocation

3. Dislocation network (δ) DO cB D D (δ) (6) C (b) (c)

3. Dislocation network

() [0] B (b) OB B aCda

4 D D B D D (b) D aD PD B A (c)

4

at (a) AB: SD()->r+DD BC: SD(a)->da+aD CA:D(B)B→B+BD at (d) AD: D+DB=yB=BC 3 BD: aD+ Dy=ay=CA 3 CD: BD+Da=Ba=AB 3

CA D D BC D D AB D D a                   ⎯→ + ⎯→ + ⎯→ + : ( ) : ( ) : ( ) at ( ) CD D D AB BD D D CA AD D D BC d 3 1 : 3 1 : 3 1 : at ( ) + = = + = = + = =            

35. 20 Simple App l icat ions of Dislocation Theory I Crystal Growth and Inter facia Structure 1. Crystal Growth Vapor— Solid; Liquid—- Solid G ap G=H-TS △Ghi=Gl-Gvap △G=VAGn1+Sy≤0

§5.20 Simple Applications of Dislocation Theory ◆ Ⅰ.Crystal Growth and Interfacial Structure 1. Crystal Growth Vapor —— Solid ; Liquid —— Solid G To T Gvap Gsol 0 chi chi sol vap  =  +   = − = − G V G S G G G G H TS