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Misfit dislocation structures are investigated in a nickel-based single crystal superalloy subjected to 38.8 h creep at 1100 °C and 130 MPa using conventional and high resolution transmission electron microscopy (HRTEM). The misfit dislocation was identified as an uncommon one with Burgers vector b = a/2 [ 2 ¯ 11 ] , which can be described as inserting (or extracting) one ( 1 1 ¯ 1 ) half plane and one ( 11 1 ¯ ) half plane. This dislocation was decomposed into two partial dislocations b 1 and b 2 , with b 1  = a/2 [ 1 ¯ 01 ] and b 2  = a/2 [ 1 ¯ 10 ] . Partial dislocations b 1 and b 2 were arranged in a “V” shape, connected by the antiphase boundary (APB), which could hinder the dislocation motion to achieve the effect of dislocation enhancement. [ABSTRACT FROM AUTHOR]

Detailed characterizations of interfacial dislocation networks in a nickel-base single crystal superalloy after creep loading for 85 h at 1100 °Cand 130 MPa were carried out at larger magnifications. The “square-like” dislocation network is formed by dislocation reaction including a[010], a/2[110], a / 2 [ 1 1 ¯ 0 ] dislocations and is different from square (and hexagonal) networks in formation mechanism and geometric structure. The atomic structure of core region of dislocations indicates their individual features and highlights the three-dimensional geometry of “square-like” dislocation network for the first time. [ABSTRACT FROM AUTHOR]

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]