The role of competing mechanisms in the fatigue life variability of a nearly fully-lamellar ?-TiAl based alloy

Jha, S. K.; Larsen, J. M.; Rosenberger, A. H.

doi:10.1016/j.actamat.2004.11.022

Cited by 51 publications

(40 citation statements)

References 14 publications

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“…The nearly flat S-N curve that is commonly reported for γ -TiAl alloys has been shown by Jha et al [67] and elsewhere [68] to be characteristic of crack initiation both at the surfaces, and in the bulk. In itself, this distinction of flaw location is not novel.…”

Section: Fatigue Crack Nucleation Mechanisms In γ -Tial Alloysmentioning

confidence: 78%

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: Fatigue Crack Nucleation Mechanisms In γ -Tial Alloysmentioning

confidence: 78%

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

Edwards

2018

Materials Science and Technology

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“…2. This separation in fatigue lifetimes, known as bimodal or competing-modes fatigue, has been observed in a wide range of alloys, including the superalloys: Rene'95 [21,22], Rene'88DT [23], IN100 [8,[24][25][26][27][28][29], Waspaloy [30], the single crystal alloy PWA 1484 [31], the titanium alloys Ti-10-2-3 [23,[32][33][34], Ti-6Al-2Sn-4Zr-6Mo [35][36][37][38][39][40][41][42], Ti-6Al-4V [43][44][45][46][47], gamma titanium aluminides [48,49], the aluminum alloy 7075-T651 [50], and others. Although such a separation of fatigue response has been known for some time [51], the significance of this behavior has not yet been generally captured in the strategies for fatigue design of turbine engine materials.…”

Section: Life Limits and Competing-mode Of Fatiguementioning

confidence: 99%

Reducing uncertainty in fatigue life limits of turbine engine alloys

Larsen

Jha

Szczepanski

et al. 2013

International Journal of Fatigue

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a b s t r a c tIn probabilistic design of materials for fracture-critical components in modern military turbine engines, a typical maximum design target risk (DTR) is 5 Â 10 À8 component failures/engine flight hour. This metric underscores the essential role of safety in a design process that simultaneously strives to achieve performance, efficiency, reliability, and affordability throughout the life cycle of the engine. Traditionally, the design and life management approaches for engine materials have typically relied on extensive testing programs to produce large databases of fatigue data, from which statistically based life limits are derived by extrapolation from the mean fatigue behavior. However, we have found that the statistical behavior of fatigue lifetimes under a given test condition often exhibits a bimodal form, and that the trends in mean vs. minimum fatigue lifetime typically respond differently to loading or to microstructural variables. Under such circumstances, the underlying life-limiting mechanisms appear to exhibit a probabilistic microstructural hierarchy in fatigue resistance that is controlled by susceptibility of local microstructural neighborhoods to early damage and the growth of small cracks. These findings suggest that significant opportunities may exist for reductions in uncertainty in materials life-cycle prediction and management, if such hierarchies can be understood and controlled. This paper explores the potential implications of these findings, and a number of possible approaches are suggested for incorporating the insights of life-limiting fatigue into methods of integrated computational materials engineering (ICME) to support optimized life-cycle design of materials and components in turbine engines. Benefits of this approach appear to include substantial improvements in model accuracy, coupled with reduced requirements for materials testing, potentially leading to a significant reduction in the time and cost to develop, validate, transition, and implement new, more fatigue resistant alloys. Published by Elsevier Ltd.

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“…25,26 The Ti-6-2-4-6 microstructure had a duplex nature and consisted of equiaxed primary-α particles and lamellar α/transformed-β ҏ regions. 25 The structure of the γ-TiAl-based alloy was nearly fully lamellar and consisted of colonies of α 2 and γ lamellae and equiaxed γ and the β phase along colony boundaries.…”

Section: Materials and Experimental Proceduresmentioning

confidence: 99%

“…25 The structure of the γ-TiAl-based alloy was nearly fully lamellar and consisted of colonies of α 2 and γ lamellae and equiaxed γ and the β phase along colony boundaries. 26 The fatigue specimens were electro-discharge machined from the same parent disk of the respective materials and from approximately the same location. The fi nal machining was done by low-stress grinding.…”

Section: Materials and Experimental Proceduresmentioning

confidence: 99%

The role of competing mechanisms in the fatigue-life variability of a titanium and gamma-TiAl alloy

Jha

Larsen

Rosenberger

2005

JOM

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Titanium Research SummaryThe variability in fatigue lives of an α+β titanium alloy ) and a γ-TiAl-based alloy in stress vs. life space resulted from superposition of variability associated with two separate mechanisms. The mean lives of the two mechanisms diverged with decreasing stress level, giving rise to the variability. A life-prediction methodology based on the variability in the worst-case mechanism is suggested. The potential for reducing uncertainty and increasing the utilization of the useful life as compared to more traditional approaches is discussed.

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The role of competing mechanisms in the fatigue life variability of a nearly fully-lamellar ?-TiAl based alloy

Cited by 51 publications

References 14 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

Reducing uncertainty in fatigue life limits of turbine engine alloys

The role of competing mechanisms in the fatigue-life variability of a titanium and gamma-TiAl alloy

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