Twinning propensity in nanocrystalline face-centered cubic, body-centered cubic, and hexagonal close-packed metals

• The twinning in nanocrystalline (nc) materials with different crystal structures is considered.
• The grain size range of the twinning propensity and twin propagation stress is analyzed.
• Calculation are made for nc fcc metals, nc bcc metals, and for nc hcp metals.
• Results are presented for the nc metals: Al,Cu,Ni,Pd,Au,Ag,Ta,Fe,Nb,Mo,Co,Zr,Mg,Ti.

The nanotwinned structures in metals exhibit the unique combination of physical properties. The unifying approach is developed that can be applied to nanocrystalline (nc) materials with different crystal structures. It is used to make a bridge between microscopical mechanisms of twin nucleation and macroscopic characteristics of the twinning and calculate them. The grain size range of the nanotwinning propensity, the grain size of its peak, and the requisite external twinning stress are calculated for the nc face-centered cubic metals Al, Cu, Ni, Pd, Au, Ag, for nc body-centered cubic metals Ta, Fe, Nb, Mo, and for hexagonal close-packed nc metals Co, Zr, Mg, Ti.