5 Werkstofftechnik
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Erscheinungsjahr
- 2022 (3) (entfernen)
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- Englisch (3)
Referierte Publikation
- ja (3)
Schlagworte
- Carbide phase NbC (1)
- Creep under thermal cycling (1)
- Crystal lattice period (1)
- Dimensional mismatch of crystalline lattice periods (misfit) (1)
- Heat-resistant nickel alloys (1)
- High temperature nickel-based eutectic alloys (1)
- High temperatures (1)
- In-situ composites (1)
- Microstructure evolution (1)
- Nickel-based superalloys (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (3) (entfernen)
A nickel-based eutectic alloy with a γ/γ'-NbC structure was directionally solidified with a planar front. The specimens were tested for creep under sawtooth thermal cycling in the temperature range from 600 to 1100°C. It has been established that the lifetime under the conditions of thermal cycling is about five times shorter than it is predicted by the linear damage accumulation rule on the basis of results of isothermal creep tests. Faster creep under thermal cycling is caused by the rapid coarsening of the γ/γ' microstructure due to the periodic partial dissolution and reprecipitation of the γ' phase in heating and cooling half-cycles.
The temperature dependences of the periods of the crystal lattices of the γ and γ' phases, their dimensional mismatch (misfit), and volume fraction of the γ' phase of an experimental single-crystal hightemperature nickel-based alloy have been determined by X-ray diffraction analysis in the temperature range of 18–1150°C. The temperature ranges in which intense changes in the structural and phase characteristics of the alloy under study take place have been determined.
An analytical model for forecasting the temperature dependence of γ/γ' misfit in heat-resistant nickel alloys is proposed. The model accounts for the concentration dependences of the periods of crystalline lattices of the γ and γ' phases (Vegard law), thermal expansion of the γ and γ' lattices, and dissolution of the γ' phase at high temperatures. Adequacy of calculations of misfit is confirmed by comparison with the results of measurements using methods of X-ray and neutron diffraction. The model is applied for development of a nickel alloy with positive misfit.