Theoretical study of the effects of alloying elements on Cu nanotwins

Nanotwins form in many metallic materials to improve their strength and toughness. In this study, we thoroughly studied the alloying effects of 10 common metal and nonmetal elements on Cu nanotwins by density functional theory (DFT). We calculated the segregation energies to determine if Cu nanotwins attract both the metal and nonmetal alloying elements; these segregation energies were then decomposed to mechanical and chemical components. The Cu-Sn bonds are different from other metal alloying elements, and the strong bond between Cu and the nonmetal element results in the negative values of the chemical contribution. Furthermore, the temperature and concentration have different effects on the nanotwin formation energy of the metal and nonmetal alloying elements. As determined by the Generalized Stacking Fault Energy, Al and nonmetals can inhibit the migration of Cu nanotwin boundary, and the effects of Li, Mg, and Sn are opposite. Our theoretical study serves as the foundation for the engineering nanotwin structures through alloying elements, the elements that may lead to new alloy compositions and thermomechanical processes, and are important complements to the experimental research.