The Effect of Ru on the Evolution of the gamma ' Phase in Ni-Al-Ru Alloys

With the development and wide application of nickel-based single-crystal superalloys, the effect of Ru on the microstructure stability and high-temperature properties of superalloys is becoming increasingly important. In this study, the effect of Ru on the evolution of the gamma ' phase in Ni-Al-Ru ternary alloys during aging treatment was analyzed, using a scanning electron microscope and transmission electron microscope, combined with energy-dispersive spectroscopy. The relationship between chemical partition behavior and gamma/gamma ' lattice misfit was investigated in detail. During the aging process, Ru addition suppressed the growth rate and rafting process of gamma ' precipitates, while the effect of Ru on hindering gamma ' phase growth was reduced when the Ru content was over 3 at%. Ru preferentially partitioned to the gamma phase, and its partitioning ratio to the gamma phase increased with a variation in Ru content from 1 at% to 3 at% and decreased for the NiAl6Ru alloy. Additionally, the lattice misfit of all alloys was positive and reduced with the increase in Ru content, which hindered the Ru atoms to diffuse into the gamma phase and promoted the shape of gamma ' precipitates to change from cubic to spherical.