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.
Highlights
The new generation Ni-base single crystal superalloys that are used to make turbine blades in aero engines show a significant improvement of the mechanical properties at high temperatures when adding specific solid solution elements, such as Re and W [1,2,3]
We focused on the effect of the excess volume of Re and W on creep deformation in Ni-base single crystal superalloys to elucidate its role in solid solution strengthening
The parelastic interaction between solute atoms and dislocations due to the excess volume of large atoms in the host matrix was implemented in a 3D discrete dislocation dynamics model
Summary
The new generation Ni-base single crystal superalloys that are used to make turbine blades in aero engines show a significant improvement of the mechanical properties at high temperatures when adding specific solid solution elements, such as Re and W [1,2,3]. The cuboidal γ0 precipitates with a high volume fraction separated by the narrow γ matrix channels form the typical microstructure of superalloy single crystals [4]. Both the γ/γ0 microstructure and dislocation motion inside are influenced by these elements. The mobility of vacancies is hardly influenced by the solute atoms within the dilute limit [15], but the low stacking fault energy induced by the solute atoms can raise the migration energy of vacancies to hinder dislocation climb [9]. Discussions about the effect of solute atoms in superalloys, especially
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