Defect based micromechanical modelling and simulation of nanoSPD CP-Ti in post-deformation

The paper concerns the dislocation based modelling and simulation of room temperature post-compression hardening after warm equal channel angular processing (ECAP) of grade 2 CP-Ti. The post-deformation behaviour is well simulated by the Zehetbauer model which already succeeded in describing the evolution of strength and structural parameters during conventional and severe plastic deformation. The model yields excellent fits to the experimental post-compression hardening characteristics (stages II, III and IV) as well as to the evolution of dislocation density. The physical quantities involved in the resulting fit parameters take reasonable values. In particular, the calculations yield a satisfactory agreement with the experimentally gained data of the cell size and the concentration of lattice vacancies, as it is shown by comparisons with X-ray profile investigations and measurements of residual electrical resistivity. As a difference to previous modelling of large strain hardening, edge dislocation density saturates at smaller strains than screw density which seems to be a consequence of the much finer initial grain structure and of the elevated ECAP deformation temperature.