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Abstract

Ni-base (or Co-base) single crystal superalloys are mainly applied as turbine blades in the hottest regions of gas turbines, due to their outstanding creep deformation resistance. In the characteristic γ/γ’ microstructure of single crystal superalloys, the lattice mismatch of these two phases results in a significant misfit stress field, which plays a decisive role for the micromechanical processes which lead to the observed macroscopic athermal deformation behavior of these high-temperature alloys. The sign and magnitude of this lattice mismatch depend on the chemical composition of materials as well as on the temperature. All currently used Ni-base superalloys possess a negative lattice misfit that becomes more negative with increasing temperature, while recently developed Co-base superalloys with a similar γ/γ’ microstructure have a positive lattice mismatch that decreases at higher temperatures.