Effects of grain size and precipitate size on the fatigue crack growth behavior of alloy 718 at 427 °C

Krueger, D. D.; Antolovich, Stephen D.; Stone, R. H. Van

doi:10.1007/bf02646657

Cited by 67 publications

(33 citation statements)

References 28 publications

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“…It is well known that grain size has an influence on the slip planarity of the Ni-based superalloys. The coarse grained microstructure is related to the enhanced slip planarity as it provides a longer free slip length for dislocations, and produces longer but more widespread slip bands associated with heterogeneous deformation compared with the fine grained counterpart [19,22]. The long and widespread slip bands usually act as a favourable stress concentrator, and thereby cause significant strain localisation as more intense back-and-forth dislocation movement is expected to be confined within this region and more dislocations are expected to pile up within the long slip band.…”

Section: Factors Controlling Crack Initiationmentioning

confidence: 99%

“…Furthermore, the long, intense and widespread slip bands in the CG LSHR are associated with more dislocation pile ups at grain boundaries, which results in higher stress concentration and thereby activates dislocation sources in the adjacent grains, facilitating crack propagation [19,22,24]. However, the coarse grained microstructure is also likely exhibit enhanced slip planarity and hence slip reversibility, which usually produce less strain accumulation within the slip bands, leading to better intrinsic crack growth resistance [11,14].…”

Section: Effects Of Microstructure On Short Crack Propagationmentioning

confidence: 99%

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Effects of microstructures on fatigue crack initiation and short crack propagation at room temperature in an advanced disc superalloy

Jiang

Karpasitis

Gao

et al. 2015

Materials Science and Engineering: A

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Fatigue crack initiation and early short crack propagation behaviour in two microstructural variants of a recently developed Low Solvus, High Refractory (LSHR) disc superalloy at room temperature has been investigated by three-point bending with replication procedure.The results shows that fine gained (FG) LSHR possesses higher fatigue life due to its better crack initiation resistance, limited crack coalescence and comparable Stage I crack propagation resistance to the coarse grained (CG) LSHR, although its resistance to Stage II crack propagation is inferior. Twin boundary (TB) cracking in the relatively large grains dominates the crack initiation process along with occasional crack initiation due to slip band cracking. Activation of the primary slip systems parallel to the TB at matrix and twin and high resolved shear stress associated with high Schmid factor (SF) are required for TB crack initiation. Cracks preferentially propagate along slip bands associated with high SF slip systems after initiation. But cracks also propagate along slip bands associated with slip systems with lower SF if the inclination angle between the slip band ahead of the crack tip and the crack segment of the crack tip is small enough to enable a steady transition (or nondeflected growth) of cracks across the grain boundary.

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Section: Factors Controlling Crack Initiationmentioning

confidence: 99%

Section: Effects Of Microstructure On Short Crack Propagationmentioning

confidence: 99%

Effects of microstructures on fatigue crack initiation and short crack propagation at room temperature in an advanced disc superalloy

Jiang

Karpasitis

Gao

et al. 2015

Materials Science and Engineering: A

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“…However, the trend shown in figure 22 suggests that this is probably not operative in most Ni-base alloys. It has also been shown that microstructural effects persist in the mid-to-high K regime for FCP of IN 718 [55]. A more complete discussion of the pros and cons of crack closure on FCP is presented elsewhere [25].…”

Section: µMmentioning

confidence: 99%

Microstructural aspects of fatigue in Ni-base superalloys

Antolovich

2015

Phil. Trans. R. Soc. A.

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Nickel-base superalloys are primarily used as components in jet engines and land-based turbines. While compositionally complex, they are microstructurally simple, consisting of small (50–1000 nm diameter), ordered, coherent Ni 3 (Al,Ti)-type L1 2 or Ni 3 Nb-type DO 22 precipitates (called γ ′ and γ ′′ , respectively) embedded in an FCC substitutional solid solution consisting primarily of Ni and other elements which confer desired properties depending upon the application. The grain size may vary from as small as 2 μm for powder metallurgy alloys used in discs to single crystals the actual size of the component for turbine blades. The fatigue behaviour depends upon the microstructure, deformation mode, environment and cycle time. In many cases, it can be controlled or modified through small changes in composition which may dramatically change the mechanism of damage accumulation and the fatigue life. In this paper, the fundamental microstructural, compositional, environmental and deformation mode factors which affect fatigue behaviour are critically reviewed. Connections are made across a range of studies to provide more insight. Modern approaches are pointed out in which the wealth of available microstructural, deformation and damage information is used for computerized life prediction. The paper ends with a discussion of the very important and highly practical subject of thermo-mechanical fatigue (TMF). It is shown that physics-based modelling leads to significantly improved life prediction. Suggestions are made for moving forward on the critical subject of TMF life prediction in notched components.

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“…Many investigators have shown grain size to have an effect on FCP rates [19][20][21][22][23][24]. In general, it appears that Increasing the grain size reduces the FCP resistance of the material, however, the mechanism for this behavior is still debated.…”

Section: Grain Sizementioning

confidence: 99%

The Effect of Microstructure on the Fatigue Crack Growth Resistance of Nickel Base Superalloys.

Antolovich¹

1987

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-U 7 b TEE EFFECT OF MICROSTRUCTURE ON THE FATIGUE CRACK GROWTH RESISTANCE OF NICKEL BASE SUPERALLOYSBased on the FCP response of these alloys it was determined that crack closure concepts did not explain the differences in FCP rates in the model Ni-base alloys studied. FCP rates were dramatically reduced for those compositions and heat treatments that promoted planar, reversible slip. The alloys having high volume fraction, low APSE, and low mismatch exhibited FCP rates that were approximately 50 times lower than other treatments. CC 0% 0%Accession For NTSGRA&1

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Effects of grain size and precipitate size on the fatigue crack growth behavior of alloy 718 at 427 °C

Cited by 67 publications

References 28 publications

Effects of microstructures on fatigue crack initiation and short crack propagation at room temperature in an advanced disc superalloy

Effects of microstructures on fatigue crack initiation and short crack propagation at room temperature in an advanced disc superalloy

Microstructural aspects of fatigue in Ni-base superalloys

The Effect of Microstructure on the Fatigue Crack Growth Resistance of Nickel Base Superalloys.

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