Experimental investigations and discrete dislocation analyses were made of plastic deformation in metallic thin films. Columnar grains which were representative of the film microstructure were considered, and simulations were based upon the assumptions that sources were scarce in geometrically-limited systems and that nucleation sites were located mainly at grain boundaries. In particular, the influence of the film thickness and grain size upon the mesoscopic constitutive response was investigated. The simulated plastic response qualitatively reproduced the experimentally observed size-effects while the main deformation mechanisms appeared to be in agreement with transmission electron microscopic analyses of test samples. A new interpretation of size scale plasticity was proposed which was based upon the probability of activating grain-boundary dislocation sources. The key role played by a parameter such as the grain aspect-ratio was highlighted. The unloading behavior was investigated, and a strong size-dependent Bauschinger effect was found. The interpretation of these phenomena was based upon an analysis of the back-stress distribution within the samples.

Discrete Dislocation Dynamics Simulations to Interpret Plasticity Size and Surface Effects in Freestanding FCC Thin Films. H.D.Espinosa, M.Panico, S.Berbenni, K.W.Schwarz: International Journal of Plasticity, 2006, 22[11], 2091-117