Chapter 5. Imperfections in Solids

1. Points Defects

2 Li D f t (Di l ti )2. Linear Defects (Dislocation)

3. Interfacial Defects

P i t D f tPoints Defects ()

1) (vacancy)

cf) (void) , , , ,

2) (interstial atom) (interstitial site)

( 2 )

3) (substitutional atom)3) (substitutional atom) 2

Self-interstitial

Substitutional InterstitialImpurity atom Impurity atom

, , ,

1) Frankel defect + antiFrankel defect +

< ( Frankel defect .)

2) Schottky defect + 2) Schottky defect +

Frankel Schottky Schottky > Frankel > anti-Frankel

anion cation substitutionalinterstitial

Schottky defect(cation vacancy +anion vacancy)

Frankel defect(anion vacancy+ interstitial cation)

(stoichiometry) /

( : nonstoichimetry)

(nonstoichimetry)

2 ..

Fe3+

(FeO, wustite)

Fe 2 (Fe3+ Fe2+)Fe3+

Fe2+Fe2+

Vacancy

(Fe , Fe ),

2 Fe3+

O2-Fe2+

(Fe1-xO)

I it i lid

Impurity in solids

99.9999% 1022~1023 /m3

(alloy)(alloy)

() (solid solution)

: () () ()

S lid S l ti

Solid Solutions

- ( )

A() - B()

(solubility limit)A B B-B eg B eg. B

1 (primary solid solution)

AmBn ( ) 2 (secondary solid solution)

1) (interstitial solid solution)

(H, O, N, C, B )

ex) Fe C, N (interstitial site)

( )( )

2) (substitutional solid solution)2) (substitutional solid solution)

,

( (ex. Cu-Ni))

(stoichiometric)

(CuZn, CuAu, Cu3Au)

( , , 3 )

-

Ex 5.3) CAl=97wt% and CCu=3wt%

Di l ti

/

Dislocation

(edge dislocation)

-

(screw dislocation)

- - ,

(mixed dislocation)

-

TEM TEM

Ed Di l ti

Edge Dislocation

: positive ti: negative

(dislocation line)

(dislocation line) (dislocation line)

Two-dimensional bubble raft model

S Di l tiScrew Dislocation

( S ) ( ) ( )

(dislocation line) (dislocation line)

(dislocation line) (dislocation line)

S

Burgers vector, vector

br

Burgers circuit vector

Mi d Di l ti

Mixed Dislocation

E S E S

br E

ebr

br

mb b

r

sb

b

r b

S

Mi d Di l tiMixed Dislocation

Di l i Dislocation

) ) T

() (loop)

) ) (low angle tilt boundary)

) :

) () :

Interfacial Defects

(external surface) ( )

(grain boundary)

(stacking fault)g

(twin boundary)

(phase boundary)

(external surface)

(broken bonds) (, J/m2 or erg/cm2)

( ) ( )

( i b d ) (grain boundary) (grain)

( l t lli t ) (polycrystalline aggregate)

: (grain) : (grain boundary)

(single crystal) ( ) ( )

Mo

MgO

( : 10 ~ 15)

(low-angle boundary) (high-angle boundary)

(dislocation array)

, (tilt boundary) (twist boundary) (mixed boundary) ( y)

(symmetric boundary) (symmetric boundary)

(asymmetric boundary)

(low-angle boundary) vs (high-angle boundary)

(stacking fault) (stacking fault)

,

, ,

= 0

S F( )

S.F.

intrinsic : intrinsic : extrinsic :

Extrinsic fault : ABCABACABC

Intrinsic fault : ABCA CABC fcc

Intrinsic fault Extrinsic fault

(twin boundary) (twin boundary)

( ) ( )

/2 /2

t bt.b.

Al2O3

(coherent boundary) (incoherent boundary)

(deformation twin) bcc, hcp (annealing twin) fcc

(phase boundary) (phase boundary)

, multiphase

Microscopic Examination

G i Si l Di l ti I di id l At / t lM i

Microscopic Examination

Grain structure

Single grain

Dislocationcells

Individualdislocations

Atom/crystalstructure

Macroscopicstructure

10 cm 0.1 mm 10 m 0.1 m 10 nm 5

Grain size determinationGrain size determination intercept method

= l = l

7

7 7 6 6

= n

: D

: MMn

lD

=

) M = 100X, l = 10 cm, n = 6.5

1530153010lD m153cm 0153.01005.6

==

=

=Mn

D

ASTM (American Society for Testing and Materials) method

grain size number : 1 ~ 10

(number size)

100X number

n : grain size number

N : 100X

12 = nN

) ASTM E112 96e1 : Standard Test Methods for Determining Average Grain Size ) ASTM E112-96e1 : Standard Test Methods for Determining Average Grain Size