Micro- and Macromechanical Properties of Fully Densified Nanocrystalline Metals

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We propose to study the fundamentals of plastic deformation in fully dense bulk nanocrystalline (nc) metals with a mean grain size between 10 and 30 nm prepared by an innovative and new combination of Inert Gas Condensation (IGC) and subsequent densification by Severe Plastic Deformation (SPD) or rolling. The model system to be investigated is Pd (fcc) and several single-phase Pd alloys. The experiments will focus on mechanical tests using new testing equipment for miniaturized specimens with stress state conditions, strain rate and temperature as the variables. The aim is to obtain a significantly improved database of materials behaviour for these alloys at this very small grain size, since this has previously been explored only sporadically, and to elucidate and describe - in the form of a deformation mechanism map with the grain size, strain rate, and temperature as the parameters - the microscopic mechanisms that mediate the deformation. Special emphasis will be addressed to in situ investigation of mesoscopic effects in plastic flow of nanocrystalline materials, such as formation of shear bands and/or cooperative grain boundary sliding, and quantitative and qualitative fractography investigations. The obtained results will be important not only for fundamental material science, but also will allow to elaborate the principles of development of technically feasible nanostructured materials providing the highest level of strength and ductility of these materials.