Analysis of single crystalline microwires under torsion using a dislocation-based continuum formulation

Abstract

In the course of structural component miniaturization, the interest in the material behavior at small scales and underlying physical mechanisms has significantly grown in the last years. In this context, the consideration of dislocations plays an essential role for the analysis of the resulting plasticity and dislocation based simulations can give helpful insights into the material evolution. In this paper, a three-dimensional crystal plasticity continuum formulation is extended by a homogenized, mechanism based dislocation source model and applied to ⟨1 0 0⟩ oriented single crystalline microwires under torsion. Fundamental operating principles of the individual slip systems, their interaction concerning the type of dislocations, relaxation mechanisms as well as the significance for the local misorientation are studied. Considering the torsion of a 24 μm thick aluminum wire, the spatial distribution of strains and dislocation densities as well as the resultant local misorientation are shown compared to discrete dislocation dynamics simulations and experiments. The results show that characteristic spatial distributions of dislocation density over the cross section can be found. Due to internal dislocation pile-ups, a size effect for small microwires under torsion can be observed.