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Mechanical Properties of Metal Nanowires and Nanoporous Foams

Brian Derby

School of Materials, University of Manchester,
Grosvenor St., Manchester, M1 7HS, UK

Recently there have been a number of reports of a very large yield stress when single crystal columns with diameter < 10-6 m are tested in compression. Similar yield stress values in excess of 1 GPa have also been observed with the plastic deformation of nanoporous gold, where the internal ligaments of the foam have a diameter < 10-7 m. Current models for this behaviour are based on concepts of the absence of dislocation sources and surface nucleation of dislocations, to explain the high plastic yield stress. Our recent results show that in nanoporous foams there are significant populations of geometrically necessary dislocations and some of the observed hardening can be explained through strain gradient models. However, nanowires deformed by up to 30% plastic strain in compression do not show significant dislocation densities indicating that distinct mechanisms of strengthening operate in nanowires and nanoporous foams. Finally it will be shown that there is a universal scaled strength of nanowires as a function of normalised wire diameter for a range of different metals.





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