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

Abstract

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 μm. 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 μm to the sub-micrometre scale (about 0.5 μm).

Keywords:

• dislocation structures
• nanoscale
• TEM
• twin thickness
• crystal orientation

Acknowledgements

This research was supported by the National Basic Research Program of China (973 Program, 2012CB932202), National Nature Science Foundation of China [grant number 51101163], [grant number 50911130230], [grant number 11374028], [grant number U1330112]; the Cheung Kong Scholars Programme of China. The authors acknowledge the Danish National Research Foundation [grant number DNRF86-5] and Natural Science Foundation of China [grant number 51261130091] for supporting the Danish-Chinese Center for Nanometals, within which part of the present work was performed.