Electron microscopy study of nanocrystalline copper deformed by a microhardness indenter

The internal structure of nanocrystalline Cu near microhardness indentations was examined by electron microscopy. In addition to observing grain growth, the number of low-angle grain boundaries was seen to increase with indenter dwell time and decreasing temperature, suggesting stress-driven grain growth by grain rotation and coalescence. Dislocation structures and deformation twins are described. No impurities could be detected at grain boundaries.