Temporal evolution of the γ(fcc)/γ′(L12) interfacial width in binary Ni–Al alloys

Plotnikov, Elizaveta Y.; Mao, Zugang; Noebe, Ronald D.; Seidman, David N.

doi:10.1016/j.scriptamat.2013.09.016

Cited by 48 publications

(31 citation statements)

References 41 publications

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“…This is consistent with the studies of Ni-Al, [48] Ni-AlCr, [49] and Ni-Al-Cr-Ta [20] alloys, which showed rapid decreases in the interface widths in the early stages of aging and lower rates of decrease with prolonged time at temperature, as the precipitates entered the coarsening regime. However, it is noted that the opposite behavior of increasing interfacial width has been reported during the aging of secondary γ′ precipitates in the commercial superalloy Rene 88DT.…”

Section: B Precipitate Compositionsupporting

confidence: 92%

Gamma Prime Precipitate Evolution During Aging of a Model Nickel-Based Superalloy

Goodfellow

Galindo-Nava

Christofidou

et al. 2017

Metall Mater Trans A

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The microstructural stability of nickel-based superalloys is critical for maintaining alloy performance during service in gas turbine engines. In this study, the precipitate evolution in a model polycrystalline Ni-based superalloy during aging to 1000 hours has been studied via transmission electron microscopy, atom probe tomography, and neutron diffraction. Variations in phase composition and precipitate morphology, size, and volume fraction were observed during aging, while the constrained lattice misfit remained constant at approximately zero. The experimental composition of the γ matrix phase was consistent with thermodynamic equilibrium predictions, while significant differences were identified between the experimental and predicted results from the γ′ phase. These results have implications for the evolution of mechanical properties in service and their prediction using modeling methods.

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Section: B Precipitate Compositionsupporting

confidence: 92%

Gamma Prime Precipitate Evolution During Aging of a Model Nickel-Based Superalloy

Goodfellow

Galindo-Nava

Christofidou

et al. 2017

Metall Mater Trans A

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“…With the alloys all having different γ/γ lattice misfit, it is important to take this property into account as well. Furthermore, the interfacial boundary width in superalloys has been shown to increase with temperature [36,37], which may explain in part the difference between the mean gradient widths in the base and '2Ta' alloys.…”

Section: Discussionmentioning

confidence: 99%

“…In this case the coefficient in the numerator of Equation (2) is 64 rather than 8 [27,30]. Alternatively, the radius of a sphere with equivalent volume is calculated [37], which is the method used in this study. All γ precipitates were assumed to be cubes, where the edge length, a, was calculated as the square root of the average cross-sectional area as measured by ImageJ, giving the following expression for the equivalent radius, r. r = a 3 4π…”

Section: Sem Analysis Of Coarsening Behaviourmentioning

confidence: 99%

Coarsening behaviour and interfacial structure of γ′ precipitates in Co-Al-W based superalloys

Vorontsov¹,

Barnard

Rahman³

et al. 2016

Acta Materialia

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This work discusses the effects of alloying on the coarsening behaviour of the L1 2 ordered γ phase and the structure of the γ/γ interfaces in three Co-Al-W base superalloys aged at ∼90 • C below the respective solvus temperatures: Co-7Al-7W, Co10Al-5W-2Ta and Co-7Al-7W-20Ni (at.%). The coarsening kinetics are adequately characterised by the classical Lifshitz-Slyozov-Wagner model for Ostwald ripening. Co-7Al-7W exhibited much slower coarsening than its quaternary derivatives. Alloying can be exploited to modify the coarsening kinetics either by increasing the solvus temperature by adding tantalum, or by adding nickel to shift the rate controlling mechanism towards dependence on the diffusion of aluminium rather than tungsten. Lattice resolution STEM imaging was used to measure the widths of the order-disorder (structural) and Z-contrast (compositional) gradients across the γ/γ interfaces. Similarly to nickel base superalloys, the compositional gradient was found to be wider than the structural. Co-7Al-7W-20Ni had much wider interface gradients than Co-7Al-7W and Co-10Al-5W-2Ta, which suggests that its γ phase stoichiometry is less constrained. A possible correlation between temperature and misfit normalised r vs. t 1 3 coarsening rate coefficients and the structural gradient width has also been identified, whereby alloys with wider interfaces exhibit faster coarsening rates.

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“…We know that c/c 0 interfaces are diffuse in multicomponent Ni-based alloys [24][25][26][27][28] as well as in binary Ni-Al alloys where the evidence is experimental [29] and computational [14,30]. We also know that the diffusion coefficients in Ni 3 Al are between one and two orders of magnitude smaller than in NiAl solid solutions at temperatures of typical coarsening experiments (800-1000 K) [31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

“…That situation has changed to a large extent with the results of several investigations in which measurements of d with t have been reported [28,29,45]. Plotnikov et al [29] published data showing that d for the Ni-Al/Ni 3 Al interface decreases rapidly at small particle sizes, the order of the interface width, and continues to decrease slightly during the coarsening Figure 2 Data on the rate constants for coarsening, k(f e ), of c (Ni-Al or Ni-Ge) precipitates in ''inverse'' a Ni 3 Al [40] and b Ni 3 Ge [41] alloys.…”

Section: Introductionmentioning

confidence: 99%

Non-integer temporal exponents in trans-interface diffusion-controlled coarsening

Ardell

2016

J Mater Sci

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The kinetics of c 0 -type (Ni 3 X) precipitate growth and solute depletion in Ni-Al, Ni-Ga, Ni-Ge, Ni-Si, Ni-Ti and Ni-Al-Cr alloys is successfully predicted by the trans-interface diffusion-controlled theory of coarsening using non-integer temporal exponents, n, satisfying 2 B n B 3, which are obtained from analyses of particle size distributions (PSDs). The origin of non-integer n is concentrationdependent diffusion through the c/c 0 interface. The literature on diffusion of Al and Ni in Ni 3 Al is specifically examined. It is shown unequivocally that the concentration-dependent diffusion of Al can account semi-quantitatively for the value of n that successfully describes the PSDs and kinetics of coarsening of the c 0 precipitates. There is no need to invoke a particle size-dependent c/c 0 interface width, as was done in prior work. It is argued that existing theory and computational modeling of coarsening in systems with highly disparate diffusion mobilities in both phases do not correctly represent the mobilities in the matrix, precipitate, and interface in Ni-Al alloys. These theories predict temporal exponents satisfying 3 B n B 4, for which there is no experimental support.

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Temporal evolution of the γ(fcc)/γ′(L12) interfacial width in binary Ni–Al alloys

Cited by 48 publications

References 41 publications

Gamma Prime Precipitate Evolution During Aging of a Model Nickel-Based Superalloy

Gamma Prime Precipitate Evolution During Aging of a Model Nickel-Based Superalloy

Coarsening behaviour and interfacial structure of γ′ precipitates in Co-Al-W based superalloys

Non-integer temporal exponents in trans-interface diffusion-controlled coarsening

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