Disclinations as Carriers of Plastic Deformation

A system of four coupled rate equations for the development of the densities of mobile and redundant dislocations and of mobile and immobile disclinations with time or strain is proposed to describe the microstructure evolution up to large strains. The densities of redundant dislocations and of immobile disclinations are connected to ow stress contributions with the help of Mughrabi's composite model, a Hall-Petch type law for cell block hardening and a misorientation-related contribution for hardening due to the long-range stress elds of disclinations. The disclination concept is connrmed by showing a triple junction at the splitting point of a dense dislocation wall into a rst generation microband in 50 % cold rolled polycrystalline copper to be a defect of disclination type.