Chapter 4-

Line Defects

• are line defects,• slip between crystal planes result when dislocations move,• produce permanent (plastic) deformation.

Dislocations:

• before deformation • after deformation

slip steps

Chapter 4-

Screw Dislocation

Atomic distortion associated with a screw dislocation is shear.

There is no extra half plane. A spiral path could be traced around the dislocation line

Burger vector for Screw - b is parallel to lineDislocations play an important role in the plastic deformation of crystalline materials.

Chapter 4-

Edge & Screw Dislocation

Chapter 4-

Edge & Screw DislocationFor metals, the Burgers vector of a dislocation will be in the close packed direction and its magnitude will be equal to one inter-atomic spacingA dislocation may change its character from edge to screw to mixed within a crystal but its Burgers vector is an invariant.

Chapter 4-

Edge & Screw Dislocation