Site preference and effect on shear deformation of co-alloying elements addition to γ′-Ni₃Al phase in Ni-based single crystal superalloys

Abstract

Alloy composition design at the atomic scale is one of the key strategies for Ni-based single crystal superalloys (Ni-SCSs). In this article, the site preference of co-alloying elements Re-M (M: Cr, Mo, W or Re) in Ni₃Al system and the strengthening effects of co-alloying elements on the shear deformation resistance of Ni₃Al system are investigated using the first-principles method. It is found that the atom pairs of co-alloying elements prefer Al–Al site and the site preference of alloying elements is not affected by paired atoms. And co-alloying atom pairs occupying Ni–Ni site have a strong mutual interaction, which can be responsible for the formation of Re clusters and segregation of alloying elements. The ideal shear strength (ISS) of the quaternary Ni₃Al system enhanced greatly by co-alloying elements is at least higher 11.9% than that of any Ni₃Al system doped with single alloying elements, which indicates there are common effect among the co-alloying elements. The result of electronic structures shows that the strong interaction between the alloy atoms and their common the first nearest neighbors (FNN) Ni atoms is the common strengthening mechanism. The present article provides valuable guidelines for improving the mechanical strength of Ni-SCSs via alloy composition design.

Keywords:

• Ni₃Al
• Co-alloying elements
• Site preference
• Ideal shear strength
• The first-principles calculation

Acknowledgments

Thanks for the financial support from the National Science and Technology Major Project (2017-VI-0003-0073, 2017-VII-0008-0101), and the National Key Research and Development Program of China (2017YFB0701503) and the Fundamental Research Funds for the University of Henan Province and the Natural Science Foundation of Henan Province (182300410266). We are grateful to Prof Yunjiang Wang of Institute of Mechanics, Chinese Academy of Sciences, Mr. Sida Ma and Mr. Cong Yang of Tsinghua University and Mr. Chen Liu of Institute of metal research, Chinese Academy of Sciences for their inspiring discussions and help.