Determination of crystallographic orientation of dwell-fatigue fracture facets in Ti-6242 alloy

Sinha, V.; Mills, M.J.; Williams, James C.

doi:10.1007/s10853-006-0252-z

Cited by 81 publications

(54 citation statements)

References 10 publications

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“…The grains fracture near the (0002) plane, which has been documented [24,22,20]. The misorientation is reported to be smaller in facets formed by continuous cycling than dwell facets, but the difference in misorien-325 tation found here was too small for a clear distinction between the load regimes.…”

supporting

confidence: 50%

“…The point of fracture origin is susceptible to the loading conditions and can also occur subsurface [7]. 20 Individual cycles can leave single growth features on the fracture surface which are termed striations. During crack opening and closing, slip systems at the crack tip are activated [8,9].…”

Section: Introductionmentioning

confidence: 99%

“…Quantitative tilt fractography (QTF) was used to calculate the spatial orientation of features on the fracture surface, as described by Sinha et al [20].…”

mentioning

confidence: 99%

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Influence of complex LCF and dwell load regimes on fatigue of Ti–6Al–4V

et al. 2016

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Real components are usually subjected to variable amplitude fatigue, and yet the deformation micromechanisms that occur due to such load changes have barely been the subject of study. Here, unidirectionally rolled equiaxed Ti6Al-4V plate was subjected to mixed dwell and variable amplitude low cycle fatigue (LCF), with the finding that overloads near the yield stress were found to retard subsequent fatigue crack growth, whilst elastic underloads were found to accelerate subsequent growth. Dwell intervals were found to be especially damaging, to a far greater extent than either dwell or LCF alone. Dwell facets were found to initiate subsurface and to be smoother than LCF facets, but were otherwise similar in orientation (∼ 30 • to the loading axis) and crystallographic plane, 2-13 • from (0002). However, no alteration of the slip bands underlying striations was observed at the point of load changes using TEM. In failure investigation, striation counting is an important tool; the loading changes used were not found to affect the number of striations formed. Dislocation networks were found between similarly oriented grains in the as-received material, which disintegrated under dwell loading and at high stresses.

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Section: Introductionmentioning

confidence: 99%

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Influence of complex LCF and dwell load regimes on fatigue of Ti–6Al–4V

et al. 2016

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“…A particularly deleterious condition known as dwell fatigue occurs in alloys such as Ti-6Al-2Sn-4Zr-2Mo. [22][23][24][25] Dwell fatigue results in significantly lower lives for loading situations containing a tensile hold component. [26] We seek to leverage r(R), to identify hard orientations in the a phase, which could potentially be used to identify failure-prone grains in an aggregate.…”

Section: A Resolved Shear Stressmentioning

confidence: 99%

“…Fracture instead of slip occurs in such grains, and fracture planes have been identified as being parallel or nearly parallel to the basal plane. [22][23][24][25] Much of this work, however, implicitly assumes a uniaxial stress state regardless of orientation in the classification of hard or soft (cf. Reference 27).…”

Section: A Resolved Shear Stressmentioning

confidence: 99%

Measuring Stress Distributions in Ti-6Al-4V Using Synchrotron X-Ray Diffraction

Bernier

Park

Pilchak

et al. 2008

Metall Mater Trans A

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This article presents a quantitative strain analysis (QSA) study aimed at determining the distribution of stress states within a loaded Ti-6Al-4V specimen. Synchrotron X-rays were used to test a sample that was loaded to a uniaxial stress of 540 MPa in situ in the A2 experimental station at the Cornell High Energy Synchrotron Source (CHESS). Lattice-strain pole figures (SPFs) were measured and used to construct a lattice strain distribution function (LSDF) over the fundamental region of orientation space for each phase. A high-fidelity geometric model of the experiment was used to drastically improve the signal-to-noise ratio in the data. The threedimensional stress states at every possible orientation of each a (hcp) and b (bcc) crystal within the aggregate were calculated using the LSDF and the single-crystal moduli. The stress components varied by 300 to 500 MPa over the orientation space; it was also found that, in general, the crystal stress states were not uniaxial. The maximum shear stress resolved on the basal and prismatic slip systems of all orientations within the a phase,ŝ rss ; was calculated to illustrate the utility of this approach for better identifying ''hard'' and ''soft'' orientations within the loaded aggregate. Orientations with low values ofŝ rss ; which are potential microcrack initiation sites during dwell fatigue conditions, are considered hard and were subsequently illustrated on an electron backscatter diffraction (EBSD) map.

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Effect of Volume Fraction of Primary α Phase on Dwell and Normal Cyclic Fatigue Behavior of Ti60 Alloy

Liu¹,

Yang²,

Wang³

et al. 2016

Proceedings of the 13th World Conference on Titanium

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The dwell and normal cyclic fatigue behaviors of Ti-5.7Al-3.7Sn-3.5Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C (Ti60) forging with a bimodal microstructure at different volume fraction of primary phase (V p ) were investigated. Lower fatigue life was found under dwell fatigue condition than under normal cyclic condition regardless of the value of V p . However, dwell fatigue sensitivity tends to decrease with the decrease of V p . Interior crack initiation characterized by higher facet density was found for dwell fatigued specimens as compared to normal cyclic fatigued ones with fatigue cracks nucleating at the surface or subsurface. Fracture surface analysis based on 3D Measuring Laser Microscope indicates that cleavage occurred favorably at grains to form facets with their normal line at an angle not larger than 15° to the loading axis under dwell loading, while the angle is only less than 5° under normal cyclic loading. It was concluded that more grains involved in dwell fatigue damage which leads to lower fatigue life and higher dwell sensitivity with increase of V p and decrease of V p is helpful to alleviate this effect.

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Determination of crystallographic orientation of dwell-fatigue fracture facets in Ti-6242 alloy

Cited by 81 publications

References 10 publications

Influence of complex LCF and dwell load regimes on fatigue of Ti–6Al–4V

Influence of complex LCF and dwell load regimes on fatigue of Ti–6Al–4V

Measuring Stress Distributions in Ti-6Al-4V Using Synchrotron X-Ray Diffraction

Effect of Volume Fraction of Primary α Phase on Dwell and Normal Cyclic Fatigue Behavior of Ti60 Alloy

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