Cryogenic indentation-induced grain growth in nanotwinned copper

Nanocrystalline copper thin films with as-deposited Σ3 twin boundaries were indented while immersed in liquid nitrogen. Quantification using precession-enhanced electron diffraction determined the crystallographic texture and grain-to-grain misorientation of the undeformed, pile-up and compressed regions. Grains in the undeformed region retained a high density of Σ3 recrystallization twins, whereas the pile-up showed significant coarsening, prevalent Σ7 subgrain formation and a decrease in twin boundaries. The abnormal grain growth is attributed to a detwinning mechanism. The compressed region showed significant grain refinement.