Segregation behavior of alloying elements at Ni Σ5 [001](210) symmetrical tilt grain boundary in nickel-based superalloys and their stabilization and strengthening mechanisms for the grain boundary

To reduce or even eliminate the negative effects of grain boundaries (GBs) in nickel-based superalloys, the GB-segregation behaviors of 14 main alloying elements X of superalloys and their effects on the stability and fracture strength of Ni Σ5 [001](210) GB were systematically investigated based on the concept of GB segregation engineering (GBSE), using first-principles calculations. We found that 10 alloying elements can segregate towards the GB. Their GB-segregation tendencies increase in the order of W < Mo < Al < Mn < Cu < Ti < Ru < Ta < Hf < Zr, due to the increase in atomic radius and electronegativity differences between X and host Ni atoms. The GB energies of X-segregated GBs depend linearly on the GB segregation energies of solutes X, the stronger segregation tendency of solute X could lower the GB energy and make the GB more stable. Except Cu, the segregations of the other 9 solutes increase the GB fracture strength. The segregation-induced GB stabilizing and strengthening mechanisms were further revealed on the electronic level. This work could be beneficial for manipulating the composition, structure and properties of Ni GBs and designing Ni-based superalloys with desired performances based on the GBSE.