First-principles study of de-twinning in a FCC alloy

First-principles calculations were used to study the effects of several alloying elements X (i.e., Al, Sc, Zn, and Ce) on the de-twinning of Cu alloys. The results show that the nanotwin (Nt) formation energy of Cu-X alloy gradually decreases with the de-twinning, but Ce improve the Nt formation energy and segregation energy of Cu alloys in T4. Furthermore, charge transfer and redistribution were investigated to explore the physical mechanisms of twinning and de-twinning. When the alloying atom is introduced, a “local effect” is formed in its neighboring regions. The anisotropic distribution of the density charges around Ce improves its bonding strength with Cu atoms, while the Sc atom and Ce atom have a smaller electronegativity and a larger atomic radius, forming strong bonds and high mechanical energy.