Editing Plasticity (physics) (section)

=== In metals ===
Plasticity in a crystal of pure metal is primarily caused by two modes of deformation in the crystal lattice: slip and twinning. Slip is a shear deformation which moves the atoms through many interatomic distances relative to their initial positions.  Twinning is the plastic deformation which takes place along two planes due to a set of forces applied to a given metal piece.

Most metals show more plasticity when hot than when cold. Lead shows sufficient plasticity at room temperature, while cast iron does not possess sufficient plasticity for any forging operation even when hot.  This property is of importance in forming, shaping and extruding operations on metals. Most metals are rendered plastic by heating and hence shaped hot.

====Slip systems====
{{main|Slip (materials science)#Slip systems}}

Crystalline materials contain uniform planes of atoms organized with long-range order. Planes may slip past each other along their close-packed directions, as is shown on the slip systems page. The result is a permanent change of shape within the crystal and plastic deformation. The presence of dislocations increases the likelihood of planes.

====Reversible plasticity====
On the nanoscale the primary plastic deformation in simple [[face-centered cubic]] metals is reversible, as long as there is no material transport in form of [[Cross Slip|cross-slip]].<ref>Ziegenhain, Gerolf; and Urbassek, Herbert M.; "Reversible Plasticity in fcc metals" in ''Philosophical Magazine Letters'', 89(11):717-723, 2009 [https://dx.doi.org/10.1080/09500830903272900 DOI 10.1080/09500830903272900]</ref> [[Shape-memory alloy]]s such as Nitinol wire also exhibit a reversible form of plasticity which is more properly called [[pseudoelasticity]].

====Shear banding====
The presence of other defects within a crystal may entangle dislocations or otherwise prevent them from gliding. When this happens, plasticity is localized to particular regions in the material. For crystals, these regions of localized plasticity are called [[shear band]]s.

====Microplasticity====
Microplasticity is a local phenomenon in metals. It occurs for [[stress (physics)|stress]] values where the metal is globally in the [[Elasticity (physics)|elastic]] domain while some local areas are in the plastic domain.<ref name="Maaß2018">{{cite journal |last1=Maaß |first1=Robert |last2=Derlet |first2=Peter M. |title=Micro-plasticity and recent insights from intermittent and small-scale plasticity |journal=Acta Materialia |date=January 2018 |volume=143 |pages=338–363 |doi=10.1016/j.actamat.2017.06.023|arxiv=1704.07297 |bibcode=2018AcMat.143..338M |s2cid=119387816 }}</ref>