Zirconium-enhanced segregation tendency of solutes X and Zr-X co-segregation induced synergistic/antagonistic effects on Ni Σ5 [001](210) grain boundary

Abstract

Manipulating grain boundary (GB) segregation of alloying elements has been established as an important pathway to optimize structural materials, due to the GB segregation induced changes in material properties, whereas solute interaction effects on GB segregation and properties remain far less developed. Here, the effects of solute interactions of Zr with X (X = Zr, Re, Ta and Cu) on the segregation behavior of solutes X at the Σ5 [001](210) GB of nickel-based superalloys, GB excess energy and fracture strength were investigated detailedly from first-principles calculations. It was found that the pre-segregation of Zr at the Ni GB not only enhances the segregation ability of subsequent solutes Zr, Ta and Cu, but also induces a GB segregation of Re that prefers grain interiors originally. Zr-Zr/Ta, Zr-Re and Zr-Cu co-segregations have synergistic potentiation, antagonistic and synergistic additive effects on improving the considered GB properties, respectively. Relative to the unsegregated GB, the Zr-Zr/Ta/Re co-segregations could improve the GB stability and fracture strength simultaneously, while the Zr-Cu co-segregation could only improve the GB stability. The co-segregation induced GB stabilizing/destabilizing and strengthening/weakening mechanisms were probed. These results would provide theoretical supports for the GB segregation engineering and quantitative composition design of high-performance nickel-based superalloys.