Mechanical Properties of Nickel-Based Superalloys

Nickel-based superalloys owe their exceptional mechanical performance in extreme environments to a finely tuned two-phase microstructure. The γ matrix provides ductility and good formability, while the ordered γ′ precipitates impede dislocation motion, yielding high strength at temperatures approaching 0.8 of the melting point. Strengthening arises from solid solution alloying, precipitate hardening and work hardening under load. Long-term exposure challenges these alloys through creep, oxidation and fatigue. Creep resistance, critical for turbine blades and discs, is enhanced by refractory elements that stabilise γ′ morphology and slow diffusion. Many alloys exhibit a yield stress anomaly in which flow stress rises with temperature due to thermally activated cross-slip of superlattice dislocations. Advances in alloy design have focused on the optimisation of γ′ volume fraction, size and distribution while balancing toughness and manufacturability. Insight into antiphase boundary energies, lattice misfit and precipitate coherency has guided the development of new compositions with extended creep and fatigue lifetimes. These materials underpin global efforts in decarbonisation by enabling higher-efficiency aero-engines and power-generation technologies.

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Mechanical Properties of Nickel-Based Superalloys publication trend

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Technical terms

γ matrix: The disordered face-centred cubic nickel-rich phase that provides ductility in superalloys.

γ′ precipitate: The ordered Ni₃Al L12 phase that impedes dislocation motion and strengthens the alloy.

Antiphase boundary energy: The excess energy associated with planar defects in an ordered phase, central to order-strengthening.

Creep: Time-dependent plastic deformation under constant stress at high temperature.

Yield stress anomaly: The unusual increase in flow stress with temperature due to thermally activated dislocation mechanisms.

Crystal plasticity: A modelling approach that describes deformation based on crystallographic slip at the grain scale.

References

1. Modeling antiphase boundary energies of Ni3Al-based alloys using automated density functional theory and machine learning. npj Computational Materials (2022).
2. Effect of Alloying Elements on the High-Temperature Yielding Behavior of Multicomponent γ′-L12 Alloys. Materials (2024).
3. Morphology Dependent Flow Stress in Nickel-Based Superalloys in the Multi-Scale Crystal Plasticity Framework. Crystals (2017).