Slip (materials science)

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Schematic view of slip mechanism

Slip is the process by which plastic deformation is produced by a dislocation motion. By an external force, parts of the crystal lattice glide along each other, resulting in a changed geometry of the material. Depending on the type of lattice, different slip systems are present in the material. More specifically, slip occurs between planes containing the smallest Burgers vector. The picture on the right shows a schematic view of the slip mechanism.

1 Slip systems
- 1.1 FCC
- 1.2 BCC
- 1.3 HCP
2 See also
3 References
4 External links

[edit] Slip systems

[edit] FCC

Lattice configuration of the close packed slip plane in an FCC material. The arrow represents the burgers vector in this dislocation glide system.

Slip in FCC (face centered cubic) crystals occurs along the close packed plane. Specifically, the slip plane is of type {111}, and the direction is of type <110>. In the diagram, the specific plane and direction are (111) and [-110], respectively. Given the permutations of the slip plane types and direction types, FCC crystals have 12 slip systems. In the FCC lattice, the Burgers vector, b, can be calculated using the following equation:^[1]

$|b|= \frac {a}{2}= \frac{a}{\sqrt 2}$ ^[1]

Where a is the lattice constant of the unit cell.

Unit Cell of an FCC material.

[edit] BCC

Lattice configuration of the slip plane in a BCC material. The arrow represents the burgers vector in this dislocation glide system.

Slip in BCC (body centered cubic) crystals occurs along the plane of shortest Burgers vector as well. In the BCC crystal the slip plane is of type {110}, and the direction is of type <111>. In the diagram the specific slip plane and direction are (110) and [-111], respectively.^[1]

Metals which exhibit BCC structure include Chromium, Iron, Tungsten, and Vanadium.

Unit Cell of a BCC material.

[edit] HCP

Slip in HCP (Hexagonal Close Packed) metals is much more limited than in BCC and FCC crystal structures. This is because few active slip systems exist in HCP metals. The result of the small number of slip systems is the the metal is generally brittle.

Cadmium, Zinc, Magnesium, Titanium, and Beryllium have a slip plane at {0001} and a slip direction of [11(-2)0]. This creates a total of three slip systems, depending on orientation. (Remember that a slip system is a combination of a slip plane and a slip direction!) Other combinations are also possible.^[2]

[edit] See also

Miller indices

[edit] References

^ ^a ^b ^c Van Vliet, Krystyn J. (2006); "3.032 Mechanical Behavior of Materials", [1]
^ Callister, William D., Jr. (2007); "Materials Science and Engineering: An Introduction", ISBN:0-471-73696-1