Thermomechanical Fatigue Behavior of a Directionally Solidified Ni-Base Superalloy

Shenoy, Mahesh; Gordon, Ali P.; Neu, Richard W.

doi:10.1115/1.1924560

Cited by 74 publications

(53 citation statements)

References 20 publications

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“…In the last two decades, considerable work has been carried out to model the constitutive behaviour of the materials, which may be generally classified into the following three categories. The first category treats the material as a homogeneous single phase material where channel width, precipitate size and other specific microstructure features are not explicitly accounted for (McHugh and Mohrmann, 1997; Shenoy et al, 2005). The second considers the two-phase nature of superalloys directly (Ohashi et al, 1997;Busso et al, 2000), where the shape, dimensions and properties of both phases are taken into account as model parameters.…”

Section: Introductionmentioning

confidence: 99%

Discrete dislocation dynamics modelling of mechanical deformation of nickel-based single crystal superalloys

Huang

Tong

2012

International Journal of Plasticity

119

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• This is the author's version of a work that was accepted for publication in the journal, International Journal of Plasticity. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication.A definitive version was subsequently pub- AbstractDiscrete dislocation dynamics (DDD) has been used to model the deformation of nickelbased single crystal superalloys with a high volume fraction of precipitates at high temperature. A representative volume cell (RVC), comprising of both the precipitate and the matrix phase, was employed in the simulation where a periodic boundary condition was applied. The dislocation Frank-Read sources were randomly assigned with an initial density on the 12 octahedral slip systems in the matrix channel. Precipitate shearing by superdislocations was modelled using a back force model, and the coherency stress was considered by applying an initial internal stress field. Strain-controlled loading was applied to the RVC in the [001] direction. In addition to dislocation structure and density evolution, global stress-strain responses were also modelled considering the influence of precipitate shearing, precipitate morphology, internal microstructure scale (channel width and precipitate size) and coherency stress. A three-stage stress-strain response observed in the experiments was modelled when precipitate shearing by superdislocations was considered.The polarized dislocation structure deposited on the precipitate/matrix interface was found to be the dominant strain hardening mechanism. Internal microstructure size, precipitate shape and arrangement can significantly affect the deformation of the single crystal superalloy by changing the constraint effect and dislocation mobility. The coherency stress field has a negligible influence on the stress-strain response, at least for cuboidal precipitates considered in the simulation. Preliminary work was also carried out to simulate the cyclic deformation in a single crystal Ni-based superalloy using the DDD model, although no cyclic hardening or softening was captured due to the lack of precipitate shearing and dislocation cross slip in this alloy.

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Section: Introductionmentioning

confidence: 99%

Discrete dislocation dynamics modelling of mechanical deformation of nickel-based single crystal superalloys

Huang

Tong

2012

International Journal of Plasticity

119

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“…The crystal plasticity was applied to study creep (Zhao et al 2006), fatigue (Kiyak et al 2008), thermal-mechanical fatigue (Shenoy et al 2005), indentation (Zambaldi et al 2007) and gradient-dependent deformation (Meissonnier et al 2001) of single crystal nickel superalloys. Application of crystal plasticity was also extended to model stress-strain response and fatigue crack nucleation for polycrystalline nickel superalloy (Dunne et al 2007), with microstructure considered as one of the major factors affecting its fatigue and creep properties.…”

Section: Introductionmentioning

confidence: 99%

Modelling plastic deformation in a single-crystal nickel-based superalloy using discrete dislocation dynamics

Lin

Huang

Farukh

et al. 2016

Mech Adv Mater Mod Process

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Background: Nickel-based superalloys are usually exposed to high static or cyclic loads in non-ambient environment, so a reliable prediction of their mechanical properties, especially plastic deformation, at elevated temperature is essential for improved damage-tolerance assessment of components. Methods: In this paper, plastic deformation in a single-crystal nickel-based superalloy CMSX4 at elevated temperature was modelled using discrete dislocation dynamics (DDD). The DDD approach was implemented using a representative volume element with explicitly-introduced precipitate and periodic boundary condition. The DDD model was calibrated using stress-strain response predicted by a crystal plasticity model, validated against tensile and cyclic tests at 850°C for <001 > and <111 > crystallographic orientations, at a strain rate of 1/s. Results: The DDD model was capable to capture the global stress-strain response of the material under both monotonic and cyclic loading conditions. Considerably higher dislocation density was obtained for the <111 > orientation, indicating more plastic deformation and much lower flow stress in the material, when compared to that for <001 > orientation. Dislocation lines looped around the precipitate, and most dislocations were deposited on the surface of precipitate, forming a network of dislocation lines. Simple unloading resulted in a reduction of dislocation density. Conclusions: Plastic deformation in metallic materials is closely related to dynamics of dislocations, and the DDD approach can provide a more fundamental understanding of crystal plasticity and the evolution of heterogeneous dislocation networks, which is useful when considering such issues as the onset of damage in the material during plastic deformation.

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“…where Based on the work of Qin et al [40,41] and Shenoy et al [42], the non-schmid stress,s a ns , dependence of the octahedral slip systems is expressed as:…”

Section: Crystal Plasticity Modelsmentioning

confidence: 99%

The effects of notch size and material microstructure on the notch sensitivity factor for notched components

Owolabi

Okeyoyin

Bamiduro

et al. 2015

Engineering Fracture Mechanics

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Keywords:Nickel base superalloy Non-metallic inclusions Probabilistic framework Fatigue notch factor Crystal plasticity a b s t r a c t Nickel base superalloys are used in hot sections of gas turbine engines due to its high strength and good creep, fatigue, and corrosion resistance at high temperature. In this paper, a new probabilistic approach based on weakest-link theory that accounts for the effects of the microstructure, notch size and notch acuity is described and applied to nickel base superalloy to determine the fatigue notch factor, notch sensitivity index and the probability of forming microstructurally small crack from the notch root. The simulation results obtained from this framework are compared with experimental results and results obtained using existing classical methods for notched polycrystalline nickel base superalloys for the different notch root radii and acuities considered.

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Thermomechanical Fatigue Behavior of a Directionally Solidified Ni-Base Superalloy

Cited by 74 publications

References 20 publications

Discrete dislocation dynamics modelling of mechanical deformation of nickel-based single crystal superalloys

Discrete dislocation dynamics modelling of mechanical deformation of nickel-based single crystal superalloys

Modelling plastic deformation in a single-crystal nickel-based superalloy using discrete dislocation dynamics

The effects of notch size and material microstructure on the notch sensitivity factor for notched components

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