Screw Dislocation

SCREW DISLOCATION

1. What is Screw Dislocation?

✓ Whenever the atoms are displaced in two separate planes perpendicular to each other, the defect so produced is known as screw dislocation.

✓ In other words, the screw dislocation may be defined as the plastic movement of atoms, within the crystal, along two separate planes perpendicular to each other.

2. Phenomenon of Screw Dislocation

✓ Fig.0.30 (a) represents an isometric view of a perfect crystal. Fig.0.30 (b) shows the displacement of atoms in the region ABC.

✓ In screw dislocation, the arrangement of atoms appear like that of a screw or helical surface.

3. Observations

It can be observed in screw dislocation that the movement of dislocation takes place in a direction parallel to the slip plane.

4. Edge Dislocation Vs Screw Dislocation

The comparison between the edge and screw dislocations are presented in Table 0.4.

Table 0.4. Edge dislocation Vs Screw dislocation