Following the deformation behavior of nanocrystalline Pd films on polyimide substrates using in situ synchrotron XRD

•Tensile tests on nanocrystalline Pd films on polyimide substrates were conducted.•The deformation behavior was characterized using in situ synchrotron XRD.•Dislocation plasticity still governs the deformation in nc Pd (grain size: 50 nm).•Grain boundary-mediated deformation dominates the microplastic regime.•The deformation behavior is strongly temperature dependent.

The deformation behavior of nanocrystalline Pd films on compliant polyimide substrates is investigated using a synchrotron-based in situ tensile testing technique. The combination of analytical and physical modeling of the evolution of peak shape during deformation allows to subdivide the deformation behavior into elastic, microplastic and macroplastic deformation. The results confirm that the deformation behavior of nanocrystalline Pd in the grain size regime of 50 nm is still governed by dislocation plasticity, however, in addition, thermally activated grain boundary mediated deformation mechanisms are active. The deformation behavior of the nanocrystalline Pd films is thus given by a specific sequence of a highly heterogeneous elastic response of the nanocrystalline aggregate, its accommodation by grain boundary mediated deformation and upcoming dislocation activity within individual grains.