Slip System

Definition - What does Slip System mean?

In metallurgy, a slip system refers to slip planes or lines at which dislocation motion (or slip) occurs. It leads to plastic deformation.

In crystals, slip system is an vital mode of deformation. It is the most crucial deformation mechanism in metals and metallic alloys. To begin plastic deformation, a critical resolved shear stress is needed.

Different metals have different slip system due their different crystallographic structures.

Corrosionpedia explains Slip System

A slip system is composed of a slip plane and a slip direction. An external force causes parts of the crystal lattices to glide along each other, altering the material's geometry. Different types of lattice causes different slip systems in the material.

Both the slip planes and slip directions in a crystal have distinct crystallographic forms. The slip planes are the planes with the highest density of atoms. The direction of the slip refers to the direction in the slip plane that corresponds to one of the smallest lattice translation vectors.

There are three types of slip systems:

  • Face-centered cubic (FCC) slip- occurs along the close-packed plane. The number of slip systems in FCC crystals is 12. It includes metals like copper, aluminum, nickel, silver, etc.
  • Body-centered cubic (BCC) slip- occurs along the plane of shortest Burgers vector. they are not truly close-packed crystal structure like FCC. It requires heat to activate. Some BCC materials (such as a-Fe) can contain up to 48 slip systems.
  • Hexagonal close packed (HCP) slip- is much more limited than in BCC and FCC crystal structures. Generally, HCP crystal structures allow slip on the densely packed basal planes.

There are two types of dislocations in crystals are important: one is slip-edge dislocations and another is screw dislocations. Which type of dislocations occur largely depends on following factors:

  • the direction of the applied stress
  • temperature
  • other factors

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