Кристаллдардың құрылымдық жазықтықтарындағы сығу және пластикалық деформация

Displacement between parts of a crystal along a crystallographic plane

In materials science, slip is the large displacement of one part of a crystal relative to another part along crystallographic planes and directions. Slip occurs by the passage of dislocations on close/packed planes, which are planes containing the greatest number of atoms per area and in close packed directions (most atoms per length). Close packed planes are known as slip or glide planes. A slip system describes the set of symmetrically identical slip planes and associated family of slip directions for which dislocation motion can easily occur and lead to plastic deformation. The magnitude and direction of slip are represented by the Burgers vector, 'b'. An external force makes parts of the crystal lattice glide along each other, changing the material's geometry. A critical resolved shear stress is required to initiate a slip.

The main methods to identify the active slip system involve either slip trace analysis of single crystals or polycrystals, and high angular resolution electron backscatter diffraction elastic strain analysis, or Transmission electron microscopy diffraction imaging of dislocations. In slip trace analysis, only the slip plane is measured, and the slip direction is inferred. In zirconium, for example, this enables the identification of slip activity on a basal, prism, or 1st/2nd order pyramidal plane. In the case of a 1st order pyramidal plane trace, the slip could be in either 〈𝑎〉 or 〈𝑐 + 𝑎〉 directions; slip trace analysis cannot discriminate between these. In low symmetry crystals such as hexagonal zirconium, there could be regions of the predominantly single slip where geometrically necessary dislocations may not necessarily accumulate. Residual dislocation content does not distinguish between glissile and sessile dislocations. Glissile dislocations contribute to slip and hardening, but sessile dislocations contribute only to latent hardening. Diffraction methods cannot generally resolve the slip plane of a residual dislocation. For example, in Zr, the screw components of 〈𝑎〉 dislocations could slip on prismatic, basal, or 1st order pyramidal planes. Similarly, 〈𝑐 + 𝑎〉 screw dislocations could slip on either 1st or 2nd order pyramidal planes.