Finite element modeling of the formation of dislocation cell structures

Theories of work hardening have been based on the occurrence of dislocation cell structures whose formation has significant influence on material properties in metals. In recent decades, considerable interest has been shown in understanding the evolution of these dislocation cell structures. The dislocation cell structure was studied by simulating the distribution of the elastic strains after unloading in each grain. The changes of the elastic strains and their magnitude are usually related to dislocation density introduced by non-uniform plastic deformation. Therefore, the distribution of dislocations is indirectly reflected by the changes of the elastic strains after unloading. In the present work, the occurrence of the structures during tensile deformation was studied using finite element (FE) modeling. The deformation within several grains was considered in this FE-model. In each grain, different anisotropic elastic moduli, yield strengths and work hardening rates were taken into account. A uniaxial tensile deformation was approached. The distributions of the elastic strains after unloading were calculated. Such distribution was found to be similar to the mosaic blocks. These calculated results indicated that anisotropic materials property in metals is one of the reasons influencing the formation of dislocation cell structures.