Gleitsysteme

Gleitsysteme are the characteristic planes and directions along which dislocations glide in crystals, enabling plastic deformation. They consist of a slip plane and a slip direction and are determined by the crystal structure as well as the orientation of the applied stress. The activity of a Gleitsystem depends on the resolved shear stress on that system and the material’s critical resolved shear stress (CRSS). Schmid's law describes how the external load projects onto a given Gleitsystem to produce glide.

In face-centered cubic (FCC) crystals, there are 12 independent Gleitsysteme: the four {111} slip planes combined with three <110> slip directions on each plane (4 × 3 = 12). These abundant, easily activated Gleitsysteme account for the high ductility of many FCC metals.

In body-centered cubic (BCC) crystals, the situation is more complex and temperature dependent. Commonly activated systems include {110}<111>, {112}<111>, and {123}<111>, with multiple equivalent orientations, typically yielding a set of 12 to 24 possible Gleitsysteme depending on the crystal orientation and conditions.

In hexagonal close-packed (HCP) crystals, Gleitsysteme are more limited. The basal system {0001} with <11-20>, the prismatic system {10-10} with <11-20>, and the pyramidal system {10-11} with <11-20> are among the main active sets. Their activation is more temperature- and alloy-dependent, leading to anisotropic plasticity.

Factors influencing Gleitsystem activity include temperature, composition, interstitials and impurities, internal stresses, and strain rate. The concept is central to understanding yield strength, work hardening, and the overall plastic behavior of crystalline materials.