An electro-deposited Cu sample with a high density of nano-scale growth twins showed an ultrahigh tensile strength (about 1GPa) with a considerable plastic strain (>13%). Both the strength and the ductility increase with a decreasing twin lamellae thickness. The yield strength values follow the empirical Hall–Petch relationship for conventional polycrystalline Cu.

Tensile Properties of Copper with Nano-Scale Twins. Y.F.Shen, L.Lu, Q.H.Lu, Z.H.Jin, K.Lu: Scripta Materialia, 2005, 52[10], 989-94