Consider the following statements regarding the behavior of dislocations:

1) Only edge dislocation and mixed dislocation can have glide motion.

2) A screw dislocation cannot have glide motion.

3) Dislocation moves in the direction perpendicular to that of shear stress.

4) The motion of dislocation occurs on a slip plane that contains Burger’s vector and a direction vector.

Which of the above statements are correct?

EXPLANATION:
Dislocation: It is the boundary between slipped and unslipped portions of a crystal.

Edge dislocation: It is a linear defect that centers on the line that is defined along the end of the extra half-plane of atoms. There is distortion around the distortion line. Atoms above the plane are squeezed together and atoms below the plane are pulled apart.

Screw dislocation: In screw dislocation, the dislocations are formed as the shear stress is applied to produce the distortion. The upper front region of the crystal is shifted from one atomic distance to the right relative to the bottom portion. Dislocation lines are parallel to the applied shear stress.

Mixed dislocation: Dislocations are mostly neither a pure edge nor the pure screw dislocation, rather they are a combination of the two, the lattice distortion that is produced away from the two faces is mixed, having varying degrees of the screw and edge character.

The nature of dislocation is defined by the relative orientation of the dislocation line and the burger vector. Burger vector for edge dislocation is perpendicular to the dislocation line and for screw dislocation, it is parallel to the dislocation line. In edge dislocation there is a half-plane Edge dislocation is a linear defect that centers on the line that is defined along the end of the extra half-plane of atoms. There is distortion around the distortion line. Atoms above the plane are squeezed together and atoms below the plane are pulled apart.

Dislocation movement:

Edge dislocation moves || to the shear direction

Screw dislocation moves ⊥ to the shear direction