8 Deformation of Crystals
合集下载
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
sequence with corresponding greater ease. The configuration in the partially slipped crystal is that of an edge dislocation.
The slip plane S is defined for the edge dislocation by the dislocation vector
S
B A
d
Screw dislocation
C B A
d
Edge dislocation
glide (conservative motion) from A to B. Climb (non-conservatiove motion) from A to D or E.
C B A
d
Kink band generation
The two possible independent kink deformations
Along the chain axis only compression (-ε3), at right
G-2 Typical slip-planes and kink-bands
Slip in extended chain crystals of polyethylene
Climb of an edge dislocation would occur if the edge dislocation
moved from A to D, or A to E. A row of motifs must be added or removed in this case (non-conservation motion).
the moleccular chain axis (z-direction), slip should occur only in planes which contain the z-direction, thereby limiting slip to the planes shown in figure.
(normal to the plane of the screen) and the Burgers vector.
The understanding of slip can thus be traced to the knowledge of motion of
dislocations and the generation of dislocations. crystals, covalent bonds are usually not broken. The slip plane must thus contain the chain axis.
Pairs of edge ns gliding along slip plane produce the kink.
Generation of a kink-band
Basically it consists of creation of pairs
of opposite edge dislocations (┴ ┬) created in the slip planes travelling to the kink-band boundaries.
G-3 Motion of dislocations The motion of both an edge dislocation and
a screw dislocation from A to B (seeing next page). No creation of new volume (or collapse) is involved so that this motion is called conservation.
Possible slip-planes and kink bands
ε4 ε5 ε6 ε6
Two independent slip planes but only 3 independent deformations—
ε4,ε5,ε6.
ε1,ε2 ,ε3 dilation components −ε1,−ε2 ,−ε3 compression components
Little is known about the generation of the many
sequential dislocations necessary to achieve macroscopic deformation.
Motion of dislocations
D A B E C A B C A B C C
Increasing numbers of dislocations
increase the kink-band angle.
S
It should be noted that in macromolecular
Slip on a
molecular scale
S
A small row of “bad crystal” travel Along the slip plane
The crystal about the S Drawn defect is showing An edge dislocation
may originate as growth defects rather than deformation bands.
The detailed process occurring during slip Instead of all bonds being broken simultaneously, they are broken in
Crystallization of Linear Macromolecules
G. Deformation of crystals
G-1 Deformation of crystals Since crystals are strongly anisotropic with respect to
about x, y, z
ε4 ,ε5,ε6 shear
components
z y x
involve rotation about the backbone chain (equivalent to glide planes oblique to the chain axis). angles only dilations are possible (ε1,ε2).
Kink-bands in extended chain crystals of polyethylene
Figure
is Decorated with folded chain lamellae that clearly mark the molecular chain direction.
Figure
In case of the screw dislocation, any plane containing the
dislocation vector (and the Burgers vector) can be the slip plane. The motif moves in the direction of the Burgers vector as in the motion of the edge dislocation; the dislocation line, however, moves at right angles.
z y x
ε1,ε2 ,ε3 dilation components −ε1,−ε2 ,−ε3 compression components
about x, y, z
Before kinking, chain
axis parallel to zdirection.
ε4 ,ε5,ε6 shear
components
about x, y, z
ε4 ,ε5,ε6 shear
components
Possible slip-planes and kink bands
Before kinking, chain
ε4 ε6 -ε3 ε1 ε5 ε6 -ε3 ε2
axis parallel to z-direction.
ε1,ε2 ,ε3 dilation components −ε1,−ε2 ,−ε3 compression components
The slip plane S is defined for the edge dislocation by the dislocation vector
S
B A
d
Screw dislocation
C B A
d
Edge dislocation
glide (conservative motion) from A to B. Climb (non-conservatiove motion) from A to D or E.
C B A
d
Kink band generation
The two possible independent kink deformations
Along the chain axis only compression (-ε3), at right
G-2 Typical slip-planes and kink-bands
Slip in extended chain crystals of polyethylene
Climb of an edge dislocation would occur if the edge dislocation
moved from A to D, or A to E. A row of motifs must be added or removed in this case (non-conservation motion).
the moleccular chain axis (z-direction), slip should occur only in planes which contain the z-direction, thereby limiting slip to the planes shown in figure.
(normal to the plane of the screen) and the Burgers vector.
The understanding of slip can thus be traced to the knowledge of motion of
dislocations and the generation of dislocations. crystals, covalent bonds are usually not broken. The slip plane must thus contain the chain axis.
Pairs of edge ns gliding along slip plane produce the kink.
Generation of a kink-band
Basically it consists of creation of pairs
of opposite edge dislocations (┴ ┬) created in the slip planes travelling to the kink-band boundaries.
G-3 Motion of dislocations The motion of both an edge dislocation and
a screw dislocation from A to B (seeing next page). No creation of new volume (or collapse) is involved so that this motion is called conservation.
Possible slip-planes and kink bands
ε4 ε5 ε6 ε6
Two independent slip planes but only 3 independent deformations—
ε4,ε5,ε6.
ε1,ε2 ,ε3 dilation components −ε1,−ε2 ,−ε3 compression components
Little is known about the generation of the many
sequential dislocations necessary to achieve macroscopic deformation.
Motion of dislocations
D A B E C A B C A B C C
Increasing numbers of dislocations
increase the kink-band angle.
S
It should be noted that in macromolecular
Slip on a
molecular scale
S
A small row of “bad crystal” travel Along the slip plane
The crystal about the S Drawn defect is showing An edge dislocation
may originate as growth defects rather than deformation bands.
The detailed process occurring during slip Instead of all bonds being broken simultaneously, they are broken in
Crystallization of Linear Macromolecules
G. Deformation of crystals
G-1 Deformation of crystals Since crystals are strongly anisotropic with respect to
about x, y, z
ε4 ,ε5,ε6 shear
components
z y x
involve rotation about the backbone chain (equivalent to glide planes oblique to the chain axis). angles only dilations are possible (ε1,ε2).
Kink-bands in extended chain crystals of polyethylene
Figure
is Decorated with folded chain lamellae that clearly mark the molecular chain direction.
Figure
In case of the screw dislocation, any plane containing the
dislocation vector (and the Burgers vector) can be the slip plane. The motif moves in the direction of the Burgers vector as in the motion of the edge dislocation; the dislocation line, however, moves at right angles.
z y x
ε1,ε2 ,ε3 dilation components −ε1,−ε2 ,−ε3 compression components
about x, y, z
Before kinking, chain
axis parallel to zdirection.
ε4 ,ε5,ε6 shear
components
about x, y, z
ε4 ,ε5,ε6 shear
components
Possible slip-planes and kink bands
Before kinking, chain
ε4 ε6 -ε3 ε1 ε5 ε6 -ε3 ε2
axis parallel to z-direction.
ε1,ε2 ,ε3 dilation components −ε1,−ε2 ,−ε3 compression components