Question

What is an edge dislocation and how does it assist in the process of slip in a crystalline metal?

Answer 1

An edge dislocation is one dimensional defect where extra half-plane of atoms is in midway through the crystal, distorting nearby planes of atoms. When enough force is applied from one side of the crystal structure, this extra plane passes through planes of atoms breaking and joining bonds with them until it reaches the grain boundary.

• Plastic deformation is due to the motion of a large number of dislocations.
• Dislocations are the elementary carriers of plastic flow thus they define material mechanical properties.
• Dislocations allow deformation at much lower stress than in a perfect crystal because slip does not require all bonds across the slip line to break simultaneously, but only small fraction of the bonds are broken at any given time.

Slip mechanism in crystal system:

Atoms bonds at the center of dislocation break and restore to allow the dislocation to move, Introduction of the dislocation into a crystal, its migration (slip) through its volume and expulsion at the crystal surface lead to material plastic deformation.