Length scale effect on the deformation microstructures of grown-in twins in copper

Electrodeposited copper samples composed of columnar grains subdivided by alternating twin/matrix (T/M) lamellae have been cold rolled to 30-85% reduction in thickness. The thickness of the T/M lamellae varies over a wide range from a few nanometres to about 1 m. The deformation microstructure has been characterized systematically.

In thin T/M lamellae (below 50-100 nm) the deformation behaviours differ significantly from that of thick T/M lamellae, as the dislocation activity is concentrated at the T/M boundaries illustrated by the observations of stacking faults and Shockley partial dislocations. In thick T/M lamellae (100-1000 nm), the deformation microstructure is related to the grain orientation as also observed previously in deformed single crystals and polycrystals with a grain size at the micrometre scale.

The experiment therefore suggests that the universal structural characteristics of deformation microstructure can be extended one order of magnitude from about 5 m to the sub-micrometre scale (about 0.5 m). © 2014 Taylor & Francis.