CHAPTER 7
DISLOCATIONS AND STRENGTHENING MECHANISMS
PROBLEM SOLUTIONS
7.1
The dislocation density is just the total dislocation length per unit volume of material (in this case per
cubic millimeters).
Thus, the total length in 1000 mm
3
of material having a density of 10
5
mm
-2
is
just
10
5
mm
-2
(
)
1000 mm
3
(
)
= 10
8
mm = 10
5
m = 62 mi
Similarly, for a dislocation density of 10
9
mm
-2
, the total length is
10
9
mm
-2
(
)
1000 mm
3
(
)
= 10
12
mm = 10
9
m = 6.2 x 10
5
mi
7.2 When the two edge dislocations become aligned, a planar region of vacancies will exist between the
dislocations as:
7.3
It is possible for two screw dislocations of opposite sign to annihilate one another if their dislocation
lines are parallel.
This is demonstrated in the figure below.
1

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