No 1, Vol. 2, 2001

Disclinations in Large-Strain Plastic Deformation and Work-Hardening

M. Seefeldt

Catholic University of Leuven,
Department of Metallurgy and Materials Engineering,
Kasteelpark Arenberg 44, B-3001 Heverlee, Belgium


Large strain plastic deformation of f.c.c. metals at low homologous temperatures results in the subdivision of monocrystals or polycrystal grains into mesoscopic fragments and deformation bands. Stage IV of single crystal work-hardening and the substructural contribution to the mechanical anisotropy emerge at about the same equivalent strain at which the fragment structure becomes the dominant substructural feature. Therefore, the latter is likely to be the reason for the new features in the macroscopic mechanical response. The present paper reviews some experimental ant theoretical work on deformation banding and fragmentation as well as a recent model which tackles the fragment structure development as well as its impact on the macroscopic mechanical response with the help of disclinations. Incidental or stress-induced formation of disclination dipoles and non-conservative propagation of disclinations are considered as "nucleation and growth" mechanisms for fragment boundaries. Propagating disclinations get immobilized in fragment boundaries to form new triple junctions with orientation mismatches and thus immobile disclinations with long-range stress fields. The substructure development is described in terms of dislocation and disclination density evolution equations; the immobile defect densities are coupled to flow or critical resolved shear stress contributions.

full paper (pdf, 376 Kb)