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In a material with a lamella type of structure, the motion of edge dislocations
under stress to form tilt boundaries can give rise to an interesting plastic
deformation mode illustrated opposite.
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The top diagram shows how a macroscopic system of laminae can "kink" due
to the relative displacement of the laminae and their resulting permenant
plastic deformation. The lower diagram illustrates this same behavior at
the atomic scale.
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Dislocation generation in a lamina and their movement to form a tilt boundary
gives rise to "kink bands" in the material that are associated with delamination
cracks. Surprisingly, these cracks increase the toughness of the material
by acting as barriers to dislocation motion. |
