Are some nanotwinned fcc metals optimal for strength, ductility and grain stability?

Here we investigate whether certain face-centered cubic metals display a superior behavior of nanotwinned structures compared to others. We also address the question of an optimal lamella thickness that yields maximum strength and stability. Our analysis of the intrinsic stacking fault energies, γsfγsf, and the unstable stacking fault energies, γusγus, of Al, Pd, Cu and Ag, as well as our atomistic simulations of dislocation–twin boundary interactions in these metals, suggests an optimal behavior of nanotwinned Pd and Ag as competitive to Cu, and hence a special utility in their synthesis and further exploration. Our results also indicate that the influence of twin–twin interactions may lead to a loss of strength below a critical value of twin lamella thickness.