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The partitioning behaviors of alloying elements Cr, Co, Al, Ta, etc. on the γ and γ′ phases of high Cr-containing (∼9wt.%) nickel-base single crystal superalloys have been investigated with and without the addition of 3wt.% Ru. The “reverse partitioning effect” occurs, which means that the addition of Ru causes the partition of Cr and Co into γ′ phase, while Al an Ta concentrate into γ matrix. However, Ru promotes the precipitation of topologically close-packed (TCP) phases, since the diffusion coefficient between the TCP phase and the matrix interface increases with the diffusion behaviors of refractory elements. For the coarsening and slightly rafting of γ′ phases, the increase of elemental diffusion plays much more important role in its kinetic process than the decrease of lattice misfit. [ABSTRACT FROM AUTHOR]

Here, we investigate a new type of kink structure that is found at γ/γ′ interfaces in nickel-based single crystal superalloys. We studied these structures at the atomic and elemental level using aberration corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The core of the dislocation absorbs high-Z elements (i.e., Co and Re) that adopt hexagonal arrangements, and it extrudes elements (i.e., Ni and Al) that adopt face centered cubic (fcc) structures. High-Z elements (i.e., Ta and W) and Cr, which is a low-Z element, are stabilized in body centered cubic (bcc) arrangements; Cr tends to behave like Re. High-Z elements, which migrate and adopt a hexagonal structure, induce kink formation at γ/γ′ interfaces. This process must be analyzed to fully understand the kinetics and dynamics of creep in nickel-based single crystal superalloys. [ABSTRACT FROM AUTHOR]