The influence of crystallographic orientation on fatigue crack growth in strongly textured Ti6A14V

Bowen, A. W.

doi:10.1016/0001-6160(75)90149-2

Cited by 61 publications

(26 citation statements)

References 34 publications

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“…A similar mechanism, in which cracks grow faster through grains in some orientations than in others, has been shown to occur at longer crack lengths in Ti-6Al-4V by Bowen. [39] The b-phase orientation was not resolved with any confidence at the level of resolution at which the EBSD scan was performed; however, there were more than enough unique a variants present to calculate the b-phase orientation by assuming the Burgers orientation relationship was held during the b fi a transformation. The parent b orientation, calculated using the method of Glavicic et al, [40,41] is shown in Figure 12.…”

Section: B Fatigue Crack Initiation In Specimenmentioning

confidence: 99%

“…It is also noted that lattice rotations about [0001] are again evident within the crack tip plastic zone beneath the striations in colony 2, but no rotations are present in colony 1, which did not fail by striation growth. Bowen [39] has speculated that the crack front grows continuously through grains oriented for hai slip, while the other grains are torn as if they were being fractured during a monotonic tension test in the wake of the crack front. The fracture topography of colony 1 is consistent with this in the sense that there are no features that are clearly associated with cyclic fatigue crack propagation.…”

Section: Observations On Long Fatigue Crack Growthmentioning

confidence: 99%

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Crystallography of Fatigue Crack Initiation and Growth in Fully Lamellar Ti-6Al-4V

Pilchak

Williams

2009

Metall Mater Trans A

116

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Fatigue crack initiation in titanium alloys is typically accompanied by the formation of planar, faceted features on the fracture surface. In the present study, quantitative tilt fractography, electron backscatter diffraction (EBSD), and the focused ion beam (FIB) have been used to provide a direct link between facet topography and the underlying microstructure, including the crystallographic orientation. In contrast to previous studies, which have focused mainly on the a-phase crystal orientation and the spatial orientation of the facets, the present analysis concentrates on the features that lie in the plane of the facet and how they relate to the underlying constituent phases and their crystallographic orientations. In addition, due to the anisotropic deformation behavior of the three basal slip systems, the orientation of the b phase as it relates to facet crystallography was investigated for the first time. The implication of the b-phase orientation on fatigue crack initiation was discussed in terms of its effect on slip behavior in lamellar microstructures. The effect of the local crystallographic orientation on fatigue crack initiation was also investigated by studying cracks that initiated naturally in the earliest stages of growth, which were revealed by FIB milling. The results indicate that boundaries that are crystallographically suited for slip transfer tend to initiate fatigue cracks. Several observations on the effect of the crystallographic orientation on the propagation of long fatigue cracks were also reported.

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Section: B Fatigue Crack Initiation In Specimenmentioning

confidence: 99%

Section: Observations On Long Fatigue Crack Growthmentioning

confidence: 99%

Crystallography of Fatigue Crack Initiation and Growth in Fully Lamellar Ti-6Al-4V

Pilchak

Williams

2009

Metall Mater Trans A

116

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“…[14,15] However, in the regime of VHCF, damage accumulation will only occur if the local microstructure is suitable for irreversible slip to accumulate. In other words, microstructural heterogeneity is thought to cause scatter in fatigue lifetimes.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Influences on Very-High-Cycle Fatigue-Crack Initiation in Ti-6246

Szczepanski

Jha

Larsen

et al. 2008

Metall Mater Trans A

152

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The fatigue behavior of an alpha + beta titanium alloy, Ti-6Al-2Sn-4Zr-6Mo, has been characterized in the very-high-cycle fatigue (VHCF) regime using ultrasonic-fatigue (20 kHz) techniques. Stress levels (r max ) of 40 to 60 pct of the yield strength of this alloy have been examined. Fatigue lifetimes in the range of 10 6 to 10 9 cycles are observed, and fatigue cracks initiate from both surface and subsurface sites. This study examines the mechanisms of fatiguecrack formation by quantifying critical microstructural features observed in the fatigue-crack initiation region. The fracture surface near the fatigue-crack-initiation site was crystallographic in nature. Facets, which result from the fracture of primary alpha (a p ) grains, are associated with the crack-initiation process. The a p grains that form facets are typically larger in size than average. The spatial distribution of a p grains relative to each other observed near the initiation site did not correlate with fatigue life. Furthermore, the spatial distribution of a p grains did not provide a suitable means for discerning crack-initiation sites from randomly selected nominal areas. Stereofractography measurements have shown that the facets observed at or near the initiation sites are oriented for high shear stress; i.e., they are oriented close to 45 deg with respect to the loading axis. Furthermore, a large majority of the grains and laths near the site of crack initiation are preferentially oriented for either basal or prism slip, suggesting that regions where a p grains and a laths have similar crystallographic orientations favor crack initiation. Microtextured regions with favorable and similar orientations of a p grains and the lath a are believed to promote cyclic-strain accumulation by basal and prism slip. Orientation imaging microscopy (OIM) indicates that these facets form on the basal plane of a p grains. The absence of a significant role of spatial clustering of a p grains, coupled with the observation of regions of microtexture on the order of 300 to 500 lm supports the idea that variability in fatigue life in the very-high-cycle fatigue regime results from the variability in the nature (intensity, coherence, and size) of these microtextured regions.

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“…At small crack lengths, the presence of microtexture has been shown to support extended faceted growth over longer distances in the microstructure compared to material with randomly oriented grains 12) . At longer crack lengths, Bowen 13) showed that long crack growth rates were significantly affected by crystallographic orientation in strongly textured plate. The change in crack growth rates were correlated with changes in fracture mode and topography.…”

Section: Introductionmentioning

confidence: 99%

The Influence on Microstructure and Microtexture on Fatigue Crack Initiation and Growth in Alpha + Beta Titanium

Pilchak

Nakase

Inagaki

et al. 2011

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)Air Force Research Laboratory SPONSORING/MONITORING AGENCY ACRONYM(S) SPONSORING/MONITORING AGENCY REPORT NUMBER(S)AFRL-RX-WP-TP-2011-4374 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution unlimited. SUPPLEMENTARY NOTESThe U.S. Government is joint author of this work and has the right to use, modify, reproduce, release, perform, display or disclose the work. PA Case Number and clearance date: 88ABW-2011-2002, 21Apr 2011. Preprint journal article to be submitted to 12 th Int'l conference on Titanium. This document contains color. ABSTRACTThe strain paths and thermal cycles utilized during thermomechanical processing of two-phase alloys have a pronounced influence on the resulting distribution of grain orientations present and their spatial distribution. For example, large regions of similarly oriented α grains, commonly referred to as microtextured regions or macrozones, may persist despite the imposition of large macroscopic strains. The detrimental effect of microtexture on dwell fatigue life of high temperature alloys is well established; however, considerably less attention has been given to the effects of microtexture on fatigue life during continuous cycling . In the present work, the effects of microstructure and microtexture on the low cycle fatigue (Nf ≤ 104 cycles) behavior of Ti-6Al-4V have been characterized using electron microscopy. Microstructural parameters such as the volume fraction and size of the α phase were assessed by quantitative metallography while the contiguity of the α phase and the size and shape of the microtextured regions were investigated with electron backscatter diffraction. SUBJECT TERMSfatigue, crack initiation, crack growth, microstructure, EBSD, fractography The strain paths and thermal cycles utilized during thermomechanical processing of two-phase alloys have a pronounced influence on the resulting distribution of grain orientations present and their spatial distribution. For example, large regions of similarly oriented α grains, commonly referred to as microtextured regions or macrozones, may persist despite the imposition of large macroscopic strains. The detrimental effect of microtexture on dwell fatigue life of high temperature alloys is well established; however, considerably less attention has been given to the effects of microtexture on fatigue life during continuous cycling . In the present work, the effects of microstructure and micr...

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The influence of crystallographic orientation on fatigue crack growth in strongly textured Ti6A14V

Cited by 61 publications

References 34 publications

Crystallography of Fatigue Crack Initiation and Growth in Fully Lamellar Ti-6Al-4V

Crystallography of Fatigue Crack Initiation and Growth in Fully Lamellar Ti-6Al-4V

Microstructural Influences on Very-High-Cycle Fatigue-Crack Initiation in Ti-6246

The Influence on Microstructure and Microtexture on Fatigue Crack Initiation and Growth in Alpha + Beta Titanium

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