On the fatigue behavior of γ-based titanium aluminides: role of small cracks

Kruzic, Jamie J.; Campbell, J.P; Ritchie, Robert O.

doi:10.1016/s1359-6454(98)00409-1

Cited by 66 publications

(40 citation statements)

References 25 publications

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“…performed by Kruzic et al [41], building on preliminary work by Chan and Shih [42]. This identified small crack growth by cleavage cracking along colony and interlamellar boundaries, as well as low-index crystallographic planes within lamellae and equiaxed grains.…”

Section: Small Cracksmentioning

confidence: 97%

Recent progress in the high-cycle fatigue behaviour of γ-TiAl alloys

Edwards

2018

Materials Science and Technology

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The high-cycle fatigue (HCF) properties of γ -TiAl (gamma titanium aluminide) alloys are reviewed, particularly with regards to the deformation mechanisms active in the near-threshold cyclic loading regime. By examining the influence of lamellar orientation and thickness on the HCF threshold, in addition to more conventional microstructural considerations such as the grain size or the volume fraction of lamellar colonies, factors to improve the γ -TiAl microstructure for HCF are assessed. Finally, experimental methods and loading strategies are surveyed to identify techniques for improving HCF testing of γ -TiAl alloys. In this, we consider both the conservativism of differing approaches and the possibility to measure with suitable resolution the local mechanical behaviour under HCF of the lamellar γ -TiAl microstructure. ARTICLE HISTORY

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Section: Small Cracksmentioning

confidence: 97%

Recent progress in the high-cycle fatigue behaviour of γ-TiAl alloys

Edwards

2018

Materials Science and Technology

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“…Kruzic has pointed out that crack nucleation occurred much more readily in the lamellar microstructure compared to that of the duplex microstructure. Crack initiation in the lamellar microstructure occurrs preferentially at favourably oriented colonies where the lamellar interfaces are subjected to the highest tensile stress (interfaces w90 to the maximum tensile stress direction) or the highest shear stress (interfaces w 45 to the maximum tensile stress direction) [30]. Shibata found that for the as-cast TiAl alloy consisting predominantly of lamellar grains, fatigue cracks were initiated from cast defects.…”

Section: Fatigue Crack Initiationmentioning

confidence: 99%

High-temperature fatigue property of Ti46Al8Nb alloy with the fully lamellar microstructure

et al. 2012

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“…Tests To evaluate the smooth-bar stress-life (S-N) fatigue propat 50 Hz were performed on a standard MTS servohydraulic erties of both microstructures, fatigue tests were performed testing machine; corresponding tests at 200 to 1000 Hz were in room-temperature air (25 ЊC, 35 to 45 pct relative humidperformed on a newly developed MTS servohydraulic test ity) under load control at positive load ratios of R ϭ 0.1 frame incorporating a voice-coil servovalve. Thresholds and 0.5, on servohydraulic testing machines cycling at 25 were determined using the same procedure described for the Hz (for lives Ͻ10 6 cycles) and at 1000 Hz (for lives Ͼ 10 6 constant-R tests. Data are presented in terms of the crack cycles) on unnotched hourglass specimens with threaded growth rate per cycle (da/dN ) as a function of the stressgrip sections and minimum gage diameters of 3.0 mm (25 intensity range (⌬K ϭ K max Ϫ K min ).…”

Section: Smooth-bar Stress-life (S-n) Fatigue Testingmentioning

confidence: 99%

Influence of microstructure on high-cycle fatigue of Ti-6Al-4V: Bimodal vs. lamellar structures

Nalla

Ritchie

Boyce

et al. 2002

Metall Mater Trans A

263

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The high-cycle fatigue (HCF) of titanium alloy turbine engine components remains a principal cause of failures in military aircraft engines. A recent initiative sponsored by the United States Air Force has focused on the major drivers for such failures in Ti-6Al-4V, a commonly used turbine blade alloy, specifically for fan and compressor blades. However, as most of this research has been directed toward a single processing/heat-treated condition, the bimodal (solution-treated and overaged (STOA)) microstructure, there have been few studies to examine the role of microstructure. Accordingly, the present work examines how the overall resistance to high-cycle fatigue in Ti-6Al-4V compares between the bimodal microstructure and a coarser lamellar (␤ -annealed) microstructure. Several aspects of the HCF problem are examined. These include the question of fatigue thresholds for through-thickness large and short cracks; microstructurally small, semi-elliptical surface cracks; and cracks subjected to pure tensile (mode I) and mixed-mode (mode I ϩ II) loading over a range of load ratios (ratio of minimum to maximum load) from 0.1 to 0.98, together with the role of prior damage due to subballistic impacts (foreign-object damage (FOD)). Although differences are not large, it appears that the coarse lamellar microstructure has improved smooth-bar stress-life (S-N) properties in the HCF regime and superior resistance to fatigue-crack propagation (in pure mode I loading) in the presence of cracks that are large compared to the scale of the microstructure; however, this increased resistance to crack growth compared to the bimodal structure is eliminated at extremely high load ratios. Similarly, under mixed-mode loading, the lamellar microstructure is generally superior. In contrast, in the presence of microstructurally small cracks, there is little difference in the HCF properties of the two microstructures. Similarly, resistance to HCF failure following FOD is comparable in the two microstructures, although a higher proportion of FOD-induced microcracks are formed in the lamellar structure following high-velocity impact damage.

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On the fatigue behavior of γ-based titanium aluminides: role of small cracks

Cited by 66 publications

References 25 publications

Recent progress in the high-cycle fatigue behaviour of γ-TiAl alloys

Recent progress in the high-cycle fatigue behaviour of γ-TiAl alloys

High-temperature fatigue property of Ti46Al8Nb alloy with the fully lamellar microstructure

Influence of microstructure on high-cycle fatigue of Ti-6Al-4V: Bimodal vs. lamellar structures

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