A Tem-Based Disclination Model for the Substructure Evolution under Severe Plastic Deformation

Abstract

Physical modelling of the macroscopic mechanical properties of metallic materials requires a coupling between these properties and the underlying micro- and substructural features. The substructure development under plastic deformation up to large strains at low and intermediate temperatures is characterized by the coexistence of two substructures on different size and misorientation scales, namely of a cell structure and a fragment (cell block) structure [1,2]. While the cell structure saturates with respect to size and misorientation, the mean fragment size decreases and the mean misorientation between fragments increases monotonously. Long-range stresses are present in the cell as well as in the fragment interiors. The present model describes the cell and the fragment structure development, that means the substructure development on the microscopic and the mesoscopic length scales, through separate, but coupled evolution equations for dislocations carrying deformation and work-hardening on the microscopic scale and for disclinations carrying them on the mesoscopic scale. The authors propose non-compensated nodes of fragment (cell block) boundaries, that means triple junctions with an orientational mismatch around them, to have a disclination character, and, thereby, to be sources of long-range stresses.