Dislocation

A dislocation is a line defect in a crystal lattice. Its motion allows crystals to deform plastically at stresses far below those required to shear a perfect lattice.

Burgers vector: A vector that specifies the magnitude and direction of lattice distortion associated with a dislocation. It quantifies the displacement carried by a dislocation and helps identify its type.
Crystal lattice: A repeating three-dimensional arrangement of atoms or other constituent particles in a crystalline solid. Dislocations are deviations from this repeating arrangement.
Work hardening: An increase in a material's strength and hardness caused by plastic deformation. Plastic strain multiplies and entangles dislocations, making further motion harder.
Vacancy: A point defect created when an atom is missing from a site in a crystal lattice. Vacancies are zero-dimensional defects, though their diffusion enables dislocation climb.
Edge dislocation: A dislocation formed by an extra half-plane of atoms terminating inside a crystal. Its extra half-plane gives a simple geometric model of dislocation strain and glide.
Slip system: A combination of a crystallographic plane and direction along which a crystal can deform by slip. A dislocation usually glides along a slip plane in a slip direction.
Solid-solution strengthening: Strengthening a material by dissolving alloying atoms into its crystal lattice. Solute atoms distort the lattice and impede dislocation motion.
Grain boundary: An interface separating crystalline regions with different lattice orientations. Grain boundaries are planar defects that can block or redirect dislocations.
Screw dislocation: A dislocation whose lattice distortion forms a helical ramp around its line. Its helical geometry permits glide on multiple planes under suitable conditions.
Shear stress: Stress acting parallel to a surface or plane, tending to make adjacent material layers slide. Resolved shear stress drives dislocation motion along favorable slip systems.

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