Weighted average study of transition metal segregation at Ni grain boundaries and its effect on grain boundary cohesion

High-performance Ni-based alloys often exhibit reduced grain boundary (GB) cohesion under high-stress or elevated-temperature conditions, necessitating further enhancement. This study investigates the segregation of 18 transition elements at Ni GBs using a weighted average method combined with first-principles calculations. The results reveal that the segregation behavior of transition metal at GBs in nickel-based alloys is influenced by the GB type, temperature and initial bulk concentration. An obvious linear correlation is observed between atom probe tomography (APT) measured and density functional theory (DFT) predicted GB concentrations in nickel-based alloy 725. Notably, the GB segregations of Mn, V, Co, Nb, Ti, Mo, Fe, and Cr are found to enhance GB cohesion. The site- and GB-weighted average method provides a novel framework for cross-validating DFT simulations with experimental data.