Recent micro-pillar experiments have shown strong size effects at small pillar diameters. This ‘Smaller is stronger’ phenomenon is widely believed to involve dislocation motion, which can be studied using dislocation dynamics (DD) simulations. In the present study, we make a 3-D DD model to study the collective dislocation behavior in BCC micro-pillars under compression. Following the work of Weinberger and Cai [1], we consider a surface-controlled cross-slip process, involving image forces and non-planar core structures, that leads to multiplication without the presence of artificial pinning points. We follow both the evolution of the dislocation structure and the corresponding stress-strain relation. In an effort to make the model conform to in-situ TEM experiments that seem to show persistent plastic flow even for very small pillars and low dislocation densities, the effects of point defects on dislocation dynamics are being explored.
[1] Weinberger CR, Cai W., Proc. Natl. Acad. Sci.(2008)