Page "Dislocation" Paragraph 42

In 1934, Egon Orowan, Michael Polanyi and G. I. Taylor, roughly simultaneously, realized that plastic deformation could be explained in terms of the theory of dislocations.

Dislocations can move if the atoms from one of the surrounding planes break their bonds and rebond with the atoms at the terminating edge.

In effect, a half plane of atoms is moved in response to shear stress by breaking and reforming a line of bonds, one ( or a few ) at a time.

The energy required to break a single bond is far less than that required to break all the bonds on an entire plane of atoms at once.

Even this simple model of the force required to move a dislocation shows that plasticity is possible at much lower stresses than in a perfect crystal.

In many materials, particularly ductile materials, dislocations are the " carrier " of plastic deformation, and the energy required to move them is less than the energy required to fracture the material.

Dislocations give rise to the characteristic malleability of metals.