Grain boundary engineering (GBE) plays an important role in the design of new polycrystalline materials with enhanced mechanical properties. This approach has been shown to be very effective in design of Ni-base alloys, where grain boundary segregation is expected to play a central role in defining their mechanical behavior. In the present work, we apply a powerful combination of advanced experimental and theoretical methods to reveal the grain boundary chemistry of the 725 Ni-base alloy at the atomic level. The m…