Discrete dislocation density modelling of single phase FCC polycrystal aggregates

A new dislocation-mechanics based crystallographic theory has been developed to model the mechanical behaviour of single-phase FCC polycrystal aggregates. In the theory, dislocations are discretised into edge and screw components with intrinsically different relative mobilities and are subject to different dynamic recovery processes. The theory has been implemented within a finite-strain and rate-dependent constitutive framework, and applied to a thin polycrystal Cu specimen to investigate the effect of intragranular lattice misorientations on deformation behaviour. These misorientations are representative of low angle grain boundaries, which are known to play an important role in the microstructural evolution of polycrystals under monotonic and cyclic deformation. This study reveals that the presence of these misorientations strengthen the material response by suppressing and re-distributing the localisation of slip within the grains, as well as inhibiting the formation of sub-grains. Through the discretisation of dislocations, the model also predicts a higher proportion of edge dislocations in the vicinities of localised slip regions.