The role of slip transfer at grain boundaries in the propagation of microstructurally short fatigue cracks in Ni-based superalloys

Jiménez, María Luz Neira; Ludwig, Wolfgang; González, David; Molina-Aldareguia, J.M.

doi:10.1016/j.scriptamat.2018.11.008

Cited by 33 publications

(6 citation statements)

References 23 publications

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“…Although micro volumes with high strain concentration can form due to the obstruction of slip transmission at GBs (Fig. 4), no crack initiation was observed from these sites, which is different to the crack initiation during fatigue in some superalloys 25,26 . The fracture surface of the region with H in presence is dominated by very flat facets, as seen in Fig.…”

Section: Response Of Twin Boundary During Mechanical Loadingmentioning

confidence: 84%

Strain localisation and failure at twin-boundary complexions in nickel-based superalloys

Zhang

Yang

et al. 2020

Nat Commun

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Twin boundaries (TBs) in Ni-based superalloys are vulnerable sites for failure in demanding environments, and a current lack of mechanistic understanding hampers the reliable lifetime prediction and performance optimisation of these alloys. Here we report the discovery of an unexpected γ″ precipitation mechanism at TBs that takes the responsibility for alloy failure in demanding environments. Using multiscale microstructural and mechanical characterisations (from millimetre down to atomic level) and DFT calculations, we demonstrate that abnormal γ″ precipitation along TBs accounts for the premature dislocation activities and pronounced strain localisation associated with TBs during mechanical loading, which serves as a precursor for crack initiation. We clarify the physical origin of the TBs-related cracking at the atomic level of γ″-strengthened Ni-based superalloys in a hydrogen containing environment, and provide practical methods to mitigate the adverse effect of TBs on the performance of these alloys.

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Section: Response Of Twin Boundary During Mechanical Loadingmentioning

confidence: 84%

Strain localisation and failure at twin-boundary complexions in nickel-based superalloys

Zhang

Yang

et al. 2020

Nat Commun

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“…Although recently developed detection methodologies such as high resolution X-ray computed tomography or synchrotron radiation computed tomography can provide a fine resolution (down in some circumstances to 0.8 µm) to examine short cracks in-situ non-destructively in three dimensions (3D), these approaches are challenging to utilize in PM Ni-based superalloys due to X-ray attenuation effects and are also complex to perform at elevated temperatures in representative service environments [17,[48][49][50].…”

Section: Short Fatigue Crack Growth Mechanisms 21 Characteristics Of Short Fatigue Crack Growth and Research Methodologiesmentioning

confidence: 99%

“…In addition, secondary cracks around crack tips can be captured in better 3D detail with tomography [17], and will be helpful to assess stress redistribution at the crack tip and stress relaxation, which is closely related to the environmental damage at the crack tip and FCG. These 3D and/or 4D assessments therefore can provide more data-rich results and a more complete view of FCG behaviours [49,50,157]. Such 3D datasets can be used to construct image-based models and hence could potentially be imported into local FE analysis models to more accurately simulate FCG behaviours with incorporated visco-plasticity and/or crystal plasticity material constitutive models.…”

Section: Perspectives and Concluding Remarksmentioning

confidence: 99%

Fatigue crack growth mechanisms in powder metallurgy Ni-based superalloys—A review

Jiang

Song

Reed

2020

International Journal of Fatigue

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Powder metallurgy (PM) Ni-based superalloys are widely used for aeroengine turbine disc applications due to their excellent mechanical properties and good corrosion resistance at elevated temperatures. Understanding the fatigue crack growth (FCG) mechanisms of PM Ni-based superalloys is important for both disc alloy development and life prediction of disc components in these advanced aeroengines where damage tolerance design prevails. FCG in PM Ni-based superalloys is a complicated function of microstructure, temperature, loading conditions and environment and is usually a consequence of the synergistic effects of fatigue, creep and environmental damage. In this review, the mechanisms controlled by microstructural features including grain size, grain misorientation, γ′ size and distribution on short and long FCG behaviour in PM Ni-based superalloys are discussed. The contribution of creep and environmental damage to FCG has been critically assessed. The competing effects of mechanical damage (i.e. fatigue and creep) and environmental damage at the crack tip are microstructure-sensitive, and usually results in transition between transgranular, mixed-trans-intergranular and intergranular FCG depending on the contribution of environmental damage to FCG processes.

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“…The experimental results show that surface defects such as surface scratches and surface inclusions have a greater influence on the fatigue life, while the fatigue life of inclusions in the sample is usually longer. Jiménez et al [ 14 ] studied the crack initiation and propagation of IN718 nickel-based superalloy under low-cycle fatigue by means of auxiliary in situ diffraction and phase contrast techniques. The results show that the propagation of short cracks in the microstructure is determined by the slip transfer path through the pre-existing grain boundary.…”

Section: Introductionmentioning

confidence: 99%

Study on Microstructure and Fatigue Properties of FGH96 Nickel-Based Superalloy

et al. 2021

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In this study, using synchrotron radiation X-ray imaging, the microstructure, tensile properties, and fatigue properties of FGH96 nickel-based superalloy were tested, and the fatigue damage mechanism was analyzed. An analysis of the experimental results shows that the alloy structure is dense without voids or other defects. It was observed that the primary γ′ phase is distributed on the grain boundary in a chain shape, and the secondary γ′ phase is found inside the crystal grains. The X-ray diffraction (XRD) pattern indicates that no other phases were seen except for the γ and γ′ phases. The tensile strength of the alloy is 1570 MPa and the elongation is 12.1%. Using data fitting and calculation, it was found that the fatigue strength of the alloy under the condition of 5 × 106 cycles is 620.33 MPa. A fatigue fracture has the characteristics of secondary crack, cleavage step, fatigue stripe, tire indentation, and dimple. The fracture is a mix of cleavage fracture and ductile fracture. Through a three-dimensional reconstruction of the alloy synchrotron radiation imaging area, it was found that the internal defects are small and mostly distributed at the edge of the sample. The dimple morphology is formed by cavity aggregation and cavity germination resulting from defects in the material itself, fracture of the second-phase particles, and separation of the second-phase particles from the matrix interface. By analyzing the damage mechanism of fatigue fractures, it is concluded that the cleavage step is formed by the intersection of cleavage planes formed by branch cracks, with the main crack of the confluence extending forward to form a cleavage fracture. The crack propagation path was also analyzed, and under the action of cyclic load and tip passivation, the crack shows Z-shaped propagation.

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The role of slip transfer at grain boundaries in the propagation of microstructurally short fatigue cracks in Ni-based superalloys

Cited by 33 publications

References 23 publications

Strain localisation and failure at twin-boundary complexions in nickel-based superalloys

Strain localisation and failure at twin-boundary complexions in nickel-based superalloys

Fatigue crack growth mechanisms in powder metallurgy Ni-based superalloys—A review

Study on Microstructure and Fatigue Properties of FGH96 Nickel-Based Superalloy

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