Site Occupancy of Re Atoms in Ni₃Al(γ') and γ-γ' Phase Equilibria in Ni-Al-Re Ternary Alloys

Abstract

Alloying behaviour of (rhenium) Re in Ni-based superalloys was investigated experimentally. Firstly, the site preference, of Re Atoms in Ni₃Al(γ') which is a main strengthening phase in the superalloys, was determined by the ALCHEMI. Secondly, the partitioning ratios of alloying elements between the γ and the γ' phases, and also the phase stability in a Ni-Al-Re ternary system were examined by the EPMA analysis and the microstructural observation as well. As the result, it was shown that Re atoms located preferably in the Al site with about 5378% occupation fraction in the Ni₃Al-2mol% Re compound. The trend of the partitioning of Re atoms into the γ' phase decreased with increasing Re in Ni-Al-Re ternary alloys. In addition, the α-phase which is a Re-rich solid solution, precipitated in the Ni-Al-Re ternary alloys containing more than 2mol% Re.