High-temperature nanoindentation measurements were employed to reveal the fundamental deformation behavior of γ and γ′ single-phase in nickel-based superalloy at various temperatures. The single-crystal samples of each phase with the equilibrium chemical compositions as in the conventionally utilized alloy were used to elucidate the temperature-dependent behavior of the individual phase leading to a further interpretation of each phase effect in the intensively used dual-phase alloy. Nanoindentation tests were conducted at room and elevated temperatures on the γ and γ′ single-phase using the Berkovich diamond indenter probe, and the Hysitron's xSol800 high-temperature stage. The noiseless load-displacement curves were obtained owing to thermal stability up to 1073 K and 873 K on the γ and γ′ sample, respectively. Furthermore, load-displacement curve shows a clear plasticity initiation in a strain burst as “pop-in” on a loading segment. The number of pop-in events in load-displacement curves of both, the γ and γ′ samples, increases with temperature. The elastic modulus and hardness of the γ phase decrease as the temperature increases, while the γ′ phase demonstrates thermal stability up to 573 K, indicating the γ′ phase domination for the high-temperature property in the dual-phase alloy. At small-scale mechanical property measurements no inverse temperature dependence of hardness was detected for the γ′ phase as a consequence of the multi-axial stress state with high hydrostatic pressure. Further, real-time topographical observations of the surface with increasing temperature reflect the behaviors of slip deformation and oxidation evolution.
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