Site preference and interaction energies of Co and Cr in gamma prime Ni3Al: a first-principles study

Nickel-based superalloys are critical for aerospace and power applications due to excellent high-temperature properties. These high-temperature properties are attributed to the coherently precipitated gamma prime phase in the gamma matrix. The segregation of alloying elements between the matrix and the gamma prime phase drives precipitate misfit strains and impacts material strength. This study aims at understanding the site preference of Co and Cr within the ordered gamma prime phase. The study also calculates the interaction energy between alloying additions within the ternary systems Ni–Al–Cr and Ni–Al–Co, and the quaternary system Ni–Al–Cr–Co. It is found that Co has mixed substitution behavior between the Al and Ni sites in the gamma prime phase. The results from the Ni–Al–Cr ternary system show that two Cr atoms prefer being close to each other, with the most stable configuration of the first nearest neighbors of the Al–Al site. The interaction energies calculated from the Ni–Al–Co system show that the initial distance between two Co atoms will decide whether the two Co atoms prefer Ni–Ni or Ni–Al configuration. The study on the quaternary system Ni–Al–Cr–Co reveals that the initial configuration of Cr and Co atoms will affect the final most stable configuration. The results are found to be consistent with our previous findings. (paper)