Dislocation

Edge dislocations involve an extra half-plane of atoms inserted in the lattice, while screw dislocations are characterized by a helical arrangement of atoms. Plastic deformation proceeds by the movement (glide) of dislocations through the crystal under applied shear stress, requiring far less stress than the theoretical strength of a perfect lattice. Strengthening mechanisms such as work hardening, solid solution strengthening, and precipitate hardening all act by impeding dislocation motion, increasing the stress required for continued deformation.