The mechanical behaviour of thin nanocrystalline palladium films with an ~30 nm in plane grain size has been characterized on chip under uniaxial tension. The films exhibit a large strain hardening capacity and a significant increase in the strength with decreasing thickness. Transmission electron microscopy has revealed the presence of a moderate density of growth nanotwins interacting with dislocations. A semi-analytical grain aggregate model is proposed to investigate the impact of different contributions to the flow behaviour, involving the effect of twins, of grain size and of the presence of a thin surface layer. This model provides guidelines to optimizing the strength/ductility ratio of the films.
Colla, M.-S., Wang, B., Idrissi, H., Schryvers, D., Raskin, J.-P., & Pardoen, T. (2012). High strength-ductility of thin nanocrystalline palladium films with nanoscale twins : On-chip testing and grain aggregate model. Acta Materialia, 60(4), 1795-1806. https://doi.org/10.1016/j.actamat.2011.11.054 (Original work published 2012)