Generalised stacking fault energy of Ni-Al and Co-Al-W superalloys: Density-functional theory calculations

Hasan, Hussain S.; Mlkvik, Peter; Haynes, Peter; Vorontsov, V.A.

doi:10.1016/j.mtla.2019.100555

Cited by 25 publications

(5 citation statements)

References 78 publications

(90 reference statements)

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“…In Ni 3 Al (at x = 0), our computed energy of the intrinsic stacking fault is 0.054 J/m 2 ; this value reasonably agrees with those ranging from 0.037 to 0.092 J/m 2 in the literature [44][45][46][47][48][49][50][51]. Depending on the distance L between the periodic stacking faults in a supercell, the intrinsic stacking fault energy varies from 0.065 J/m 2 at L ≈ 10 Å to 0.054 J/m 2 at L > 40 Å; a monotonic decrease in energy with distance at L > 10 Å points at repulsion between the stacking faults.…”

Section: Resultssupporting

confidence: 88%

Energy-Composition Relations in Ni3(Al1−xXx) Phases

2023

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The secondary phase, such as Ni3Al-based L12 γ′, is crucially important for the precipitation strengthening of superalloys. Composition–structure–property relations provide useful insights for guided alloy design. Here we use density functional theory combined with the multiple scattering theory to compute dependencies of the structural energies and equilibrium volumes versus composition for ternary Ni3(Al1−xXx) alloys with X = {Ti, Zr, Hf; V, Nb, Ta; Cr, Mo, W} in L12, D024, and D019 phases with a homogeneous chemical disorder on the (Al1−xXx) sublattice. Our results provide a better understanding of the physics in Ni3Al-based precipitates and facilitate the design of next-generation nickel superalloys with precipitation strengthening.

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Section: Resultssupporting

confidence: 88%

Energy-Composition Relations in Ni3(Al1−xXx) Phases

2023

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“…The dislocation density in the γ channel decreased significantly, and the dislocations accumulated at the γ/γ interfaces and partially formed the dislocation networks. Different from cryogenic temperatures and room temperature, the γ phase was cut in the form of dislocations because of its high stacking fault energy at high temperature [23].…”

Section: Dislocation Configuration Responsementioning

confidence: 99%

“…Compared with the cryogenic temperature and room temperature, the critical shear stress of the sliding system is reduced at 1000 • C [24]; the tertiary γ phase in the γ channel dissolved, and the strength of the γ phase was greatly reduced [11,25], thus the dislocation was easy to start and had no obstruction in the γ channel. At 1000 • C, the stacking fault energy of the alloy was high [23], which means the dislocation was prone to cut in the secondary γ phase directly without stacking faults or bypassing the secondary γ phase through cross-slip, and without causing strain hardening. Therefore, the yield strength and ultimate strength decreased and the elongation rose significantly at 1000 • C in comparison with cryogenic temperatures and room temperature.…”

Section: Dislocation Configuration Responsementioning

confidence: 99%

Tensile Deformation Behavior of a Directionally Solidified Superalloy at Cryogenic Temperatures

Guo

Wang³

et al. 2022

Crystals

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Ni-based superalloys are widely used to manufacture gas turbine core components, but reports on the reliability of superalloys at cryogenic temperatures are still limited. Considering the actual application of superalloys in the field of cryogenic temperature, the tensile deformation behavior of directionally solidified superalloy DZ406 was investigated at cryogenic temperatures from −125 °C to 25 °C, and the comparative analysis of room temperature and 1000 °C was carried out. The yield strength and ultimate strength at cryogenic temperatures were close to that at room temperature, and twice that at 1000 °C. The elongation was maintained at 10–15% and exhibited a certain plasticity at cryogenic temperatures. The morphologies and chemical composition of γ′ precipitates were close at cryogenic temperatures, room temperature and 1000 °C. The microstructure difference that was caused by different temperatures was mainly reflected in the fracture mode and dislocation configuration. At cryogenic temperature, the fracture samples basically exhibited no necking phenomenon, and the cracks were basically located in the interdendritic regions and occurred in MC carbide itself; at room temperature and 1000 °C, dimples with carbides inside were distributed on the fracture surface. Slip bands and dislocations contributed to the tensile deformation at cryogenic temperatures and room temperature, while only the dislocations worked at 1000 °C.

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“…Since the configuration space to be probed is larger in CoNi-base compositions than in Co-base and Ni-base compositions, deriving PFEs from state-of-the-art methods is not trivial. Alternatively, Hasan et al (159) proposed averaging schemes using Vegard's law of mixtures to estimate PFEs from Co 3 X and Ni 3 X binary compounds. Most fault energies of multicomponent compositions calculated with this approach were negative.…”

Section: Alloying Effects In Ni- Co- and Coni-base Superalloysmentioning

confidence: 99%

Precipitate Shearing, Fault Energies, and Solute Segregation to Planar Faults in Ni-, CoNi-, and Co-Base Superalloys

Eggeler

Vamsi

Pollock

2021

Annu. Rev. Mater. Res.

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The mechanical properties of superalloys are strongly governed by the resistance to shearing of ordered precipitates by dislocations. In the operating environments of superalloys, the stresses and temperatures present during thermomechanical loading influence the dislocation shearing dynamics, which involve diffusion and segregation processes that result in a diverse array of planar defects in the ordered L12 γ′ precipitate phase. This review discusses the current understanding of high-temperature deformation mechanisms of γ′ precipitates in two-phase Ni-, Co-, and CoNi-base superalloys. The sensitivity of planar fault energies to chemical composition results in a variety of unique deformation mechanisms, and methods to determine fault energies are therefore reviewed. The degree of chemical segregation in the vicinity of planar defects reveals an apparent phase transformation within the parent γ′ phase. The kinetics of segregation to linear and planar defects play a significant role in high-temperature properties. Understanding and controlling fault energies and the associated dislocation dynamics provide a new pathway for the design of superalloys with exceptional properties.

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Generalised stacking fault energy of Ni-Al and Co-Al-W superalloys: Density-functional theory calculations

Cited by 25 publications

References 78 publications

Energy-Composition Relations in Ni3(Al1−xXx) Phases

Energy-Composition Relations in Ni3(Al1−xXx) Phases

Tensile Deformation Behavior of a Directionally Solidified Superalloy at Cryogenic Temperatures

Precipitate Shearing, Fault Energies, and Solute Segregation to Planar Faults in Ni-, CoNi-, and Co-Base Superalloys

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