Kruvidislokatsioon

Kruvidislokatsioon, commonly referred to in crystallography as a screw dislocation, is a line defect in crystalline solids characterized by a Burgers vector that runs parallel to the dislocation line. Around the dislocation core, the lattice planes twist in a helical fashion, so that a closed loop enclosing the line is shifted by an amount equal to the Burgers vector. In a pure screw dislocation, the displacement field around the line is purely rotational, with no extra lattice planes inserted or removed.

Geometrically, the dislocation line extends through the crystal, and the atomic displacement is greatest azimuthally about this line. The energy per unit length of a screw dislocation in an isotropic elastic approximation scales with the square of the Burgers vector and depends on material constants and logarithmic factors, reflecting the long-range elastic distortion of the lattice.

Formation and motion are driven by plastic deformation. Screw dislocations move by glide within their slip plane under applied shear stress. Climb, which requires diffusion of vacancies, occurs at higher temperatures and allows dislocations to bypass obstacles or react with other defects. Dislocations can cross-slip to different planes, creating complex networks that influence mechanical response.

Significance and applications: screw dislocations play a central role in determining yield strength, work hardening, ductility, and creep behavior of metals and some ceramics. Understanding their behavior aids in alloy design and in predicting material performance under load.

Observation and study methods include transmission electron microscopy, diffraction techniques, and atomic-scale simulations. The term Kruvidislokatsioon reflects a linguistic rendering of the concept, often used in contexts where “kruvi” means screw and “dislokatsioon” means dislocation.