PLASTIC DEFORMATION & DISLOCATIONS

Change in shape of single crystals (grains)

Note intersecting planes SLIP PLANES In fcc copper Note intersecting planes More than one set of (111) planes is active due to action of CRSS equation and angles on inclination to the applied stress

DISLOCATIONS EDGE DISLOCATION Extra line of atoms is present in part of the crystal Dislocation line is normal to Burgers vector Generates a compression – tension couple (i.e. stress) Tension below the dislocation Compression above the dislocation line Dislocation interacts with applied stress and moves Generates plastic deformation

Movement of an Edge Dislocation

Common in crystal growth SCREW DISLOCATION Common in crystal growth Dislocation line parallel to Burgers vector

Screw dislocation from above Open circles are atoms above dislocation line Black circles are atoms below dislocation line