A dislocation will decompose into partial dislocations if the energy state of the sum of the partials is less than the energy state of the original dislocation. This is summarized by Frank's Energy Criterion:
Shockley partial dislocationsEdit
Shockley partial dislocations generally refer to a pair of dislocations which can lead to the presence of stacking faults. This pair of partial dislocations can enable dislocation motion by allowing an alternate path for atomic motion.
In FCC systems, an example of Shockley decomposition is:
Which is energetically favorable:
The components of the Shockley Partials must add up to the original vector that is being decomposed:
Frank partial dislocationsEdit
Frank partial dislocations are sessile (immobile), but can move by diffusion of atoms. In FCC systems, Frank partials are given by:
Shockley partials and Frank partials can combine to form a Thompson tetrahedron, or a stacking fault tetrahedron.
The Lomer–Cottrell lock is formed by partial dislocations and is sessile.
^Meyers and Chawla. (1999) Mechanical Behaviors of Materials. Prentice Hall, Inc. 217.