Question

Subject: Manufacturing process

Explain the differences between Dislocations vs. Crystal Defects

Answer 1

Dislocation- It is a type of crystal defect. It comes under line defect. Dislocations are the areas where atoms aren't in their particular position,they are out of their location. This defect is caused when a stress is developed in a crystal structure. This disloction allows slip-plastic deformation to occur.

There are basically two types of dislocation ie -

1-edge dislocation -

The edge defect can be easily visualized as an extra half-plane of atoms in a lattice. The dislocation is called a line defect because the locus of defective points produced in the lattice by the dislocation lie along a line. This line runs along the top of the extra half-plane. The inter-atomic bonds are significantly distorted only in the immediate vicinity of the dislocation line.

2-screw dislocation- There is a second basic type of dislocation, called screw dislocation. The screw dislocation is slightly more difficult to visualize. The motion of a screw dislocation is also a result of shear stress, but the defect line movement is perpendicular to direction of the stress and the atom displacement, rather than parallel.

crystal defects- A perfect crystal is an idealization; there is no such thing in nature. Atom
arrangements in real materials do not follow perfect crystalline patterns.

there are vasically three types of defects ie

• point defects, which are places where an atom is missing or irregularly placed in the lattice structure. Point defects include lattice vacancies, self-interstitial atoms, substitution impurity atoms, and interstitial impurity atoms
• linear defects, which are groups of atoms in irregular positions. Linear defects are commonly called dislocations.
• planar defects, which are interfaces between homogeneous regions of the material. Planar defects include grain boundaries, stacking faults and external surfaces