Grain size effects on plastic strain and dislocation density tensor fields in metal polycrystals

A strain gradient crystal plasticity model is used to explore the grain size effect on the fields of plastic strain and of the dislocation density tensors in two-dimensional polycrystals. Finite element simulations are performed for several aggregates of 24 and 52 grains with a detailed description of the intragranular fields. It is found that the increasing energy cost associated with the development of geometrically necessary dislocations (GNDs) leads to the formation of a network of intense slip bands accommodating the imposed deformation in ultra-fine grain polycrystals.