A bulk columnar-grained copper with preferentially oriented nanoscale growth twins is prepared by means of direct-current electrodeposition. Tensile tests at different strain rates reveal a significant influence of strain rate on the tensile ductility and fracture behavior. The ductility, especially the post-necking elongation, reduces dramatically at low strain rates, which is associated with evident intergranular fracture. The results suggest that the grain size as well as the grain boundary microstructural evolution exert a strong influence on the intrinsic fracture mode in the nano-twinned structure.
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