Dislocation in Engineering Materials under various conditions

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1. Dislocation

2. Linear defect around which some of the atoms are misaligned An extra plane of atoms terminate within the crystals Called slip-plane Plastic deformation moves around this plane

3. Dislocation lines move in the direction of applied stress EDGE DISLOCATION

4. MOVEMENT OF EDGE DISLOCATION

5. Dislocation lines move perpendicular to applied stress SCREW DISLOCATION

6. Internal Energy after plastic deformation ( minus heat dissipation) Lattice strains

7. Plastic Deformation means motion of large number of dislocations More the plastic deformation less is the hardness and tensile strength of the material Reducing the mobility of dislocation means greater mechanical forces are required to initiate the plastic deformation It means increasing the strength of the metal Summary: Restricting dislocation motion makes a metal stronger

8. Grain boundary: Barrier to dislocation motion

9. Fine-grained material= greater total grain boundary area= decreased dislocation motion = harder & stronger metal