Coarsening kinetics of γ′ precipitates in the Ni–Al–Mo system

Wang, Tao; Gao, Sheng; Liu, Zhe; Chen, Lei

doi:10.1016/j.actamat.2008.07.024

Cited by 112 publications

(43 citation statements)

References 58 publications

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“…Coarsening and coalescence of γ′ precipitates, through application of the LSW theory and particle agglomeration mechanism have been studied in several research works [22,23].…”

Section: Introductionmentioning

confidence: 99%

Coarsening and dissolution of γ′ precipitates during solution treatment of AD730™ Ni-based superalloy: Mechanisms and kinetics models

Masoumi

Jahazi

Shahriari

et al. 2016

Journal of Alloys and Compounds

139

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The kinetics of γ′ size and volume fraction changes during solution treatment of the advanced Ni-based superalloy, AD730 TM are determined and the underlying mechanisms are investigated.High resolution Differential Thermal Analysis (DTA) and thermodynamic modeling were used to design and perform solution heat treatment experiments. Semi-analytical models are developed to describe the dissolution and coarsening processes. The results from the proposed models, supported by electron microscopy observations, indicate that coarsening occurs before complete dissolution takes place. Agglomeration is shown to be the governing coarsening mechanism for this alloy after calculation of the coefficients for both the Ostwald ripening and agglomeration mechanisms. Electron microscopy observations revealed that the early stages of agglomeration occur by neck formation between two neighboring particles. The splitting of γ′ particles was identified as one of the main dissolution mechanisms. Based on the obtained results, a dissolution kinetics model is proposed to quantify the volume fraction of dissolved γ′ particles and estimate the activation energy of this process for AD730 TM . A coarsening model based on the time-temperature dependence of the γ′ coarsening rate coefficient is also proposed taking the concentration of elements, γ′ volume fraction and the temperature into consideration. Based on this model, a method is developed to predict γ′ size evolution during aging heat treatment process and an optimum heat treatment to reach the desired γ′ distribution is proposed.The validity and accuracy of the proposed models were verified by carrying out different heat treatment experiments.

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“…Coarsening and coalescence of γ′ precipitates, through application of the LSW theory and particle agglomeration mechanism have been studied in several research works [22,23].…”

Section: Introductionmentioning

confidence: 99%

Coarsening and dissolution of γ′ precipitates during solution treatment of AD730™ Ni-based superalloy: Mechanisms and kinetics models

Masoumi

Jahazi

Shahriari

et al. 2016

Journal of Alloys and Compounds

139

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“…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: 95%

“…It has been reported by Wang et al that the volume fractions of the secondary phases will significant affect the coarsening rate coefficients [51].…”

Section: β-Phase Coarsening Kineticsmentioning

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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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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“…In order to affect the volume constraint as given by Eq. [29], the Lagrange parameter k b is computed as…”

Section: Conservation Of Volumementioning

confidence: 99%

“…A similar dynamic evolution model has also been used to predict equilibrium shapes in 3Ds in Reference 28. Apart from the determination of equilibrium shapes, the diffuse-interface methods have also been used for the study of growth and coarsening of multi-particle systems, [27,[29][30][31][32][33][34] instabilities, [35] and rafting. [36][37][38][39][40][41] In all the above studies, the central focus of investigation has been the study of equilibrium shapes of precipitates where the anisotropy exists only in the elastic energy.…”

Section: Introductionmentioning

confidence: 99%

Phase-Field Modeling of Equilibrium Precipitate Shapes Under the Influence of Coherency Stresses

Bhadak

Sankarasubramanian

Choudhury

2018

Metall Mater Trans A

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Coherency misfit stresses and their related anisotropies are known to influence the equilibrium shapes of precipitates. Additionally, mechanical properties of the alloys are also dependent on the shapes of the precipitates. Therefore, in order to investigate the mechanical response of a material which undergoes precipitation during heat treatment, it is important to derive the range of precipitate shapes that evolve. In this regard, several studies have been conducted in the past using sharp-interface approaches where the influence of elastic energy anisotropy on the precipitate shapes has been investigated. In this paper, we propose a diffuse interface approach which allows us to minimize grid-anisotropy-related issues applicable to sharp-interface methods. In this context, we introduce a novel phase-field method where we minimize the functional consisting of the elastic and surface energy contributions while preserving the precipitate volume. Using this technique, we reproduce the shape bifurcation diagrams for the cases of pure dilatational misfit that have been studied previously using sharp-interface methods and then extend them to include interfacial energy anisotropy with different anisotropy strengths which has not been a part of previous sharp-interface models. While we restrict ourselves to cubic anisotropies in both elastic and interfacial energies in this study, the model is generic enough to handle any combination of anisotropies in both the bulk and interfacial terms. Further, we have examined the influence of asymmetry in dilatational misfit strains along with interfacial energy anisotropy on precipitate morphologies.

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Coarsening kinetics of γ′ precipitates in the Ni–Al–Mo system

Cited by 112 publications

References 58 publications

Coarsening and dissolution of γ′ precipitates during solution treatment of AD730™ Ni-based superalloy: Mechanisms and kinetics models

Coarsening and dissolution of γ′ precipitates during solution treatment of AD730™ Ni-based superalloy: Mechanisms and kinetics models

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

Phase-Field Modeling of Equilibrium Precipitate Shapes Under the Influence of Coherency Stresses

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