The precipitation of topologically-closed-packed (TCP) phases in Ni-base single crystal superalloys was suppressed due to the Ruthenium or Iridium additions, resulting in the superior creep resistance. However, no clear explanation for such improvement in phase stability has been reported. Therefore, it's necessary to determine the underlying mechanism in the atomic scale such as short range ordering and elemental distributions in the gamma phase. The present article has investigated the effects of Ru/Ir additions on elemental distributions in gamma phase by using 3-dimensional atom probe field-ion microscopy.
The concentration frequencies of Re, W and Mo within Ru/Ir centered spheres including 100 atoms in gamma phases were analyzed statistically. The results showed that the concentration frequencies of Re, W and Mo within Ru/Ir centered spheres corresponded to binomial distributions. This indicated that the effects of Ru/Ir additions on elemental distributions in the gamma phase were not able to be detected under the condition employed in the present study.