The mechanical properties of the dislocation core

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Abstract
Dislocations are topological defects in crystal structure, with primary importance in the phenomenon of plasticity. Their presence in otherwise perfect crystals can lead to a reduction in mechanical strength by a factor of 104. Most properties of dislocations are governed by their continuum elastic strain fields and hence are independent of lattice structure. An exception to this rule is the elastic limit. Close-packed crystals yield plastically at a nearly temperature-independent stress of about 10−5p (μ is the elastic shear modulus) and show no intrinsic plastic anisotropy. Body-centred cubic crystals have an intrinsic elastic limit which depends strongly on temperature and orientation, reaching a magnitude of 5 × 10−3 μ at low temperatures and varying by a factor of three with orientation. Computer modelling suggests that the origin of this structural discrepancy lies in the dislocation core, that region close to the dislocation line in which the discreteness of the lattice becomes important and within which the elastic strains are too large to be treated by continuum elasticity.

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