Application of a modified Ostwald ripening theory in coarsening of γ′ phases in Ni based single crystal superalloys

Ai, Cheng; Zhao, Xinbao; Zhou, Jian; Zhang, Heng; Liu, Lei; Pei, Yanling; Li, Shusuo; Gong, Shengkai

doi:10.1016/j.jallcom.2015.01.215

Cited by 66 publications

(20 citation statements)

References 26 publications

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“…Therefore, in order to account the effects of β-phase volume fraction on the coarsening kinetics, a dimensionless factor as a function of β-phase volume fraction ( ) is introduced by combining the models reviewed by Baldan [39] and the most recent effort by Ai et al [50] for cubic/nearly cubic morphology of secondary phase. …”

Section: β-Phase Coarsening Kineticsmentioning

confidence: 99%

“…Lifshitz and Slyozov [44] and Wagner [45] (LSW) derived the first analytical description of particle coarsening in binary alloy systems, in which the predicted coarsening rate of the mean particle size is reported to be proportional to time 1/3 . In recent decades, the theory proposed by LSW has been extended to multicomponent alloys such as Ni superalloys [46][47][48][49][50][51][52], Ti alloys [53][54][55] and other types of alloys [56][57][58]. However, application of LSW theory to MCrAlY alloys does not appear to have been previously reported.…”

Section: Introductionmentioning

confidence: 99%

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An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

Chen

McCartney

2017

Journal of Alloys and Compounds

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This paper investigates the β-phase coarsening behaviour during isothermal heat treatment of free-standing CoNiCrAlY (Co-31.7%Ni-20.8%Cr-8.1%Al-0.5%Y, all in wt%) coatings prepared by high velocity oxy-fuel (HVOF) thermal spraying. The microstructure of the coatings was characterised using scanning electron microscopy with energy dispersive X-ray (EDX) analysis and electron backscatter diffraction (EBSD). It comprises a two phase structure of fcc γ-Ni matrix and bcc β-NiAl precipitates. The volume fraction of the γ-Ni and the β-NiAl phases were measured to be around 70% and 30% respectively, with grain sizes varying largely from 0.5 to 2 µm for both phases. Isothermal heat treatments of the freestanding coatings were carried out at 1100 C for times up to 250 h. The β-phase coarsening behaviour during isothermal heat treatments was analysed by quantitative metallography. It is shown that the coarsening behaviour of β phase in the CoNiCrAlY alloy followed the classical Lifshitz-Slyozov-Wagner (LSW) theory of Ostwald ripening. By incorporating a dimensionless factor which correlates with volume fraction of the β phase, a modified LSW model coupled with formulaic interfacial energy and effective diffusion coefficient of the 2 CoNiCrAlY alloy was utilised to interpret the coarsening behaviour of the β phase. The coarsening rate coefficient obtained from the modified LSW model shows good agreement with the corresponding experimental result.

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Section: β-Phase Coarsening Kineticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

Chen

McCartney

2017

Journal of Alloys and Compounds

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“…The models for the precipitation kinetics, including classic nucleation, diffusion controlled growth, and coarsening, are well developed [12,14,66,67,85] and have been successfully applied to simulate the γ precipitation in Ni-based superalloys [3,5,64,65,68,74]. Olson et al validated a similar precipitation model implemented in PrecipiCalc for 3rd generation disk alloys [64,65].…”

Section: γ Precipitationmentioning

confidence: 99%

“…The models for additional strengthening mechanisms, such as solid solution strengthening and Hall-Petch effect, have also been implemented based on the statistical analyses [49,73]. Using these strengthening models, the processing conditions (processing temperature and time) are chosen to maximize the yield strength of the microstructure [3,41,91].…”

Section: Yield Stressmentioning

confidence: 99%

A Computational Framework for Material Design

Kattner

Campbell

2017

Integr Mater Manuf Innov

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A computational framework is proposed that enables the integration of experimental and computational data, a variety of user-selected models, and a computer algorithm to direct a design optimization. To demonstrate this framework, a sample design of a ternary Ni-Al-Cr alloy with a high work-to-necking ratio is presented. This design example illustrates how CALPHAD phase-based, composition and temperature-dependent phase equilibria calculations and precipitation models are coupled with models for elastic and plastic deformation to calculate the stress-strain curves. A genetic algorithm then directs the search within a specific set of composition and processing constraints for the ideal composition and processing profile to optimize the mechanical properties. The initial demonstration of the framework provides a potential solution to initiate the material design process in a large space of composition and processing conditions. This framework can also be used in similar material systems or adapted for other material classes.Keywords Ni-based superalloy · Integrated computational materials engineering · Genetic algorithm · Material design

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“…However, it would be reasonable to simplify the coarsening kinetics of lamellar structures in the same way since, essentially, it is the overall interfacial energy that drives the coarsening mechanism. Recent studies [23,24] also show that the isotropic coarsening rate, as in the LSW coarsening mechanism, can be applied as an indicator of creep properties in Ni superalloys. In this model, the isotropic coarsening rate is proportional to temperature and determined by two constants, while no formal connection to the chemical composition is assumed.…”

Section: B Fan's Modelmentioning

confidence: 99%

The Compositional Dependence of the Microstructure and Properties of CMSX-4 Superalloys

Zwaag

2017

Metall Mater Trans A

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The degradation of creep resistance in Ni-based single-crystal superalloys is essentially ascribed to their microstructural evolution. Yet there is a lack of work that manages to predict (even qualitatively) the effect of alloying element concentrations on the rate of microstructural degradation. In this research, a computational model is presented to connect the rafting kinetics of Ni superalloys to their chemical composition by combining thermodynamics calculation and a modified microstructural model. To simulate the evolution of key microstructural parameters during creep, the isotropic coarsening rate and c/c¢ misfit stress are defined as composition-related parameters, and the effect of service temperature, time, and applied stress are taken into consideration. Two commercial superalloys, for which the kinetics of the rafting process are selected as the reference alloys, and the corresponding microstructural parameters are simulated and compared with experimental observations reported in the literature. The results confirm that our physical model not requiring any fitting parameters manages to predict (semiquantitatively) the microstructural parameters for different service conditions, as well as the effects of alloying element concentrations. The model can contribute to the computational design of new Ni-based superalloys.

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Application of a modified Ostwald ripening theory in coarsening of γ′ phases in Ni based single crystal superalloys

Cited by 66 publications

References 26 publications

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

A Computational Framework for Material Design

The Compositional Dependence of the Microstructure and Properties of CMSX-4 Superalloys

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