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Influence of excess volumes induced by Re and W on dislocation motion and creep in Ni-base single crystal superalloys: a 3D discrete dislocation dynamics study

S. Gao, Z. Yang, M. Grabowski, J. Rogal, R. Drautz, A. Hartmaier.

Metals, 9, 637, (2019)

Dislocation patterns in [101](-1-11) (yellow) and [101](1-1-1) (orange) slip systems in γ matrix channels after 14 s under 200 MPa tensile load along [001] direction at 850 C for different solute atoms. Dislocations are viewed in the projection on (001) crystallographic planes, corresponding to Figure 1. One dislocation line containing some dislocation jogs with another color indicates the occurrence of dislocation climb: (a) no solute atom; (b) 7 × 10−3 at.% Re; and (c) 7 × 10−3 at.% W.

Abstract
A comprehensive 3D discrete dislocation dynamics model for Ni-base single crystal superalloys was used to investigate the influence of excess volumes induced by solute atoms Re and W on dislocation motion and creep under different tensile loads at 850 C. The solute atoms were distributed homogeneously only in γ matrix channels. Their excess volumes due to the size difference from the host Ni were calculated by density functional theory. The excess volume affected dislocation glide more strongly than dislocation climb. The relative positions of dislocations and solute atoms determined the magnitude of back stresses on the dislocation motion. Without diffusion of solute atoms, it was found that W with a larger excess volume had a stronger strengthening effect than Re. With increasing concentration of solute atoms, the creep resistance increased. However, a low external stress reduced the influence of different excess volumes and different concentrations on creep.

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