A higher-order crystal plasticity model based on the continuum description of dislocation dynamics was developed to investigate the confined thin-film plasticity at micro-scale. In this model, the “back stress” and the “slip resistance” for each slip system were incorporated into a standard diffusion equation for crystal slip, which accounts for the motion of dislocations in a continuum level. Furthermore, a surface energy based interfacial model was introduced here to take account of the interaction between dislocations and the interface. It could provide a more comprehensive study of the interface effect on the confined crystal plastic behavior rather than the two extreme boundary models used in other higher-order crystal plasticity models in which the dislocations could freely or hardly pass through the crystal interface. Then by implementing these models into finite element code the tensions of single-crystal/polycrystal thin Al films with passivation layers were numerically investigated. Two hardening factors associated respectively with the “back stress” and “slip resistance” were qualitatively studied, and it could be concluded from present study that the “back stress” hardening may dominate the strengthening of flow stress in confined thin-film plasticity at sub-micro scale. The interfacial model was applied to successfully model the interactions of dislocation with the film-passivation interfaces.

A Dislocation Dynamics Based Higher-Order Crystal Plasticity Model and Applications on Confined Thin-Film Plasticity. Z.L.Liu, Z.Zhuang, X.M.Liu, X.C.Zhao, Z.H.Zhang: International Journal of Plasticity, 2011, 27[2], 201-16