材料科学基础
Fundamental of Materials
Prof,Tian Min Bo
Tel,62795426, 62772851
E-mail,tmb@mail.tsinghua.edu.cn
Department of Material Science and Engineering
Tsinghua University,Beijing 100084
Lesson twenty-four
§ 5.16 Dislocation in FCC crystals
? Ⅰ.Perfect dislocation
??? ?
??? cnbnanb
221 ???
??? 1 1 0
2
1
FC CFor
b
?
]121[61]112[61]101[21 ??
? Ⅱ.Shockley partial dislocation
AC
B
]110[21?b?
The slip movement of a perfect dislocation consists of
two steps,This can be expressed in terms of vector
combination,]121[
6
1]211[
6
1]110[
2
1 ??
The Shockley partial is the line of demarcation on slip plane
{111} between slipped and unslipped zones,the slip vector
being,
It also the boundary line between faulted and unfaulted
zones.
?? 11261
FCC {111}<112>
BCC {112}<111>
HCP ?? 1110}2110{
A
C
B
A
C
A
C
B
A
C
B
A
C
]101[ ]001[
]101[]121[21
]001[未滑 已滑
Characteristic of Shockley Partial:
1,It is the boundary between faulted and unfaulted.
2,It can be edge,screw or mixed zones dislocation.
3,Even in edge orientation,it can not climb.
Even in screw orientation,it can not cross slip.
4,It can move only on faulted plane (slip) shockley
partial,
? Ⅲ.Extended dislocation
A
A
A
A A
C
B
A
B
Bb
b1 b2
]121[
6
1
:
]112[
6
1
:
]101[
2
1
:
2
1
b
b
b
unslipped unfaultedslipped
(faulted) zones
]121[61 ]121[
6
1
I II III
1b
2b
Two parallel shockley partial dislocations separated by a
faulted zone constitute an extended dislocation.
§ 5.17 Frank Partial Dislocation in
FCC
1,Frank Partial is formed by extracting or
inserting part of {111} plane.
negative Frank positive Frank
??? 1 1 131b?
intrinsic stacking fault
??? 1 1 131b?
extrinsic stacking fault
The former is called negative Frank dislocation,While the
latter positive.
2,Movement of Frank Partial
3,Practical formation process of Frank Partial
It can only climb,slip can never occur.
A cluster of point defects preferably precipitate on
{111} ==> collapse to form disk of point defects ==>
dislocation loop
Examples and Discussions
Exercise
Thank you !
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