Solute segregation induced stabilizing and strengthening effects on Ni Σ3 [110](111) symmetrical tilt grain boundary in nickel-based superalloys

Abstract

Grain boundary segregation engineering (GBSE) is a promising approach for accurately manipulating chemical composition, structure and properties of grain boundaries (GBs). With the aim of attenuating or even removing disadvantages of GBs in nickel-based superalloys, the GB segregation behaviors of 3d (Ti–Co), 4d (Zr–Rh) and 5d (Hf–Ir) transition-metal (TM) solutes X and their effects on the thermodynamic stability and fracture strength of Ni Σ3 [110](111) symmetrical tilt grain boundary were systematically investigated, using first-principles total-energy calculations based on density functional theory. We found that all TM solutes considered herein can segregate towards the Ni Σ3 [110](111) GB. For TM elements from same row of the periodic table, their segregation energies show a concave-up parabolic-like dependency on the atomic number of TM elements. The GB segregations of all considered solutes can lead to a reduction in GB energy and render the Ni GB more stable, and the GB energies of X-segregated GBs vary linearly with the GB segregation energies of solutes X. Except elements Zr, Hf and Rh, the GB segregations of the other 15 TM alloying elements increase the GB fracture strength. The Mn and Re segregations improve the GB fracture strength and thermodynamic stability to a maximum extent, respectively. The underlying mechanisms for segregation-induced GB stabilizing and strengthening effects were further revealed at the electronic level by analyzing the crystal orbital Hamiltonian populations and deformation charge densities. Our work could provide new insights into designing Ni-based superalloys with desired performances based on the concept of GBSE.