Plastic Deformation

· In hcp crystals the basal (0001) planes in are parallel, and for the early deformation stages of an fcc crystal slip is only on parallel {111} planes.
· Frank-Reed dislocation sources on these planes will generate dislocations during plastic deformation.

· If the motion of the leading dislocation on a given plane is blocked, a "pile up" occurs on that plane .
· Elastic interactions between dislocations on this plane and those on the parallel slip planes will reduce the mobility of dislocations on those planes and require more work from the external forces to continue the deformation.

From: Hull, "Introduction to Dislocations," Pergamon (1965)