Lomer–Cottrell junction

In materials science, a Lomer–Cottrell junction is a particular configuration of dislocations that forms when two perfect dislocations interact on interacting slip planes in a crystalline material.

When the two leading Shockley partials combine, they form a separate dislocation with a burgers vector that is not in the slip plane.

For an FCC crystal with slip planes of the form {111}, consider the following reactions: The resulting dislocation lies along a crystal direction that is not a slip plane at room temperature in FCC materials.

Trailing dislocations pile up behind this junction, leading to an increase in the stress required to sustain deformation.

This mechanism is a key contributor to work hardening in ductile materials like aluminum and copper.