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TEM observations of the typical microstructure in the in situ consolidated nanocrystalline Cu. The bright-field TEM micrograph (a) and the SADP [the upper left inset in (a)] show roughly equiaxed grains with random orientations. The statistical distribution of grain size (b) was obtained from multiple dark-field TEM images of the same sample.
A typical tensile stress-strain curve for the bulk in situ consolidated nanocrystalline Cu sample in comparison with that of a coarse-grained polycrystalline Cu sample (an average grain size larger than ) and a nanocrystalline Cu sample prepared by an inert-gas condensation and compaction technique (Ref. 17) (with a mean grain size of ).
BFTEM micrographs show the dislocation activity of a nanocrystalline Cu grain during in situ TEM deformation. The loading and crack growth directions are shown at the upper and left sides of the figure, respectively. (a) The nano grain at certain straining, which shows dislocations inside the nano grain. (b) Dislocation generation and pile-up on the grain boundary upon further straining (white arrows). (c) More straining of the nano grain showing also the dislocations pile-up. (d) Further straining initiates a crack in the nano grain (black arrow), while the piled-up dislocations still exist.
A typical BFTEM micrograph of trapped dislocations in a Cu nanograin formed during in situ TEM deformation.
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