Subsurface fatigue crack initiation in beta titanium alloys

Tokaji, Keiro; Ohya, Kohji; Kariya, Hiroyasu

doi:10.1046/j.1460-2695.2000.00325.x

Cited by 28 publications

(11 citation statements)

References 10 publications

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“…[2,4,15,16] For this reason, it is important to understand how to control the amount of GBA. Figure 3 shows how Widmansta¨t-ten a phase can grow with similar growth directions from a b grain boundary that lacks a significant amount of GBA.…”

Section: Methodsmentioning

confidence: 99%

Formation of Grain Boundary α in β Ti Alloys: Its Role in Deformation and Fracture Behavior of These Alloys

Foltz

Welk

Collins

et al. 2010

Metall Mater Trans A

110

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Beta-Ti alloys contain sufficient concentrations of b stabilizing alloy additions to permit retention of the metastable b phase after cooling to room temperature. Decomposition of the metastable b phase results in the formation of several possible phases, at least two of which are metastable. Concurrently, equilibrium a phase often forms first by heterogeneous nucleation at the a grain boundaries with an accompanying precipitate free zone observed adjacent to the grain boundary a. The grain boundary regions are softer than the precipitation hardened matrix. As a consequence, fracture follows the prior b grain boundaries, especially in highstrength conditions. This fracture mode results in low tensile ductility and/or fracture toughness. This article will describe methods of minimizing or eliminating grain boundary a formation by using metastable transition precipitates to nucleate a more rapidly. The effects on fracture behavior also will be described.

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Section: Methodsmentioning

confidence: 99%

Formation of Grain Boundary α in β Ti Alloys: Its Role in Deformation and Fracture Behavior of These Alloys

Foltz

Welk

Collins

et al. 2010

Metall Mater Trans A

110

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“…Tokaji et al [37] found in an AZ31 magnesium alloy that in subsurface fracture, facets were always present at the crack initiation site, most of which were located close to the surface, and the facet sizes were nearly the same as, or smaller than, the average grain size. The same authors [38,39] observed subsurface fracture in beta titanium alloys and indicated the presence of smooth facets at the crack initiation site. Therefore, the concepts presented in this article are expected to be applicable to all metals.…”

Section: Effect Of Subsurface Crack Initiators On Fatigue Potentmentioning

confidence: 83%

Fracture Surface Facets and Fatigue Life Potential of Castings

Tiryakioğlu

Campbell

Nyahumwa

2011

Metall Mater Trans B

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Fatigue potential has been studied in cast aluminum alloys with regard to the fatigue crack initiation mechanism at the casting defects, particularly surface and subsurface defects. The significance of facets is interpreted as the presence of defects in the interior of castings. Furthermore, two varieties of facets have been identified, one originating as a dendrite-straightened bifilm (type I facet) and the other originating from a slip plane mechanism around casting defects (type II facet). The fatigue life potential of castings is reexamined based on the involvement of defects during the formation of both types of facets. It is proposed that the true fatigue life potential of defect free castings has yet to be observed, i.e., if castings can be produced without defects, then their fatigue performance will be significantly higher than even the best performances observed so far.

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“…As stated in the introduction, only a few publications mention the presence of markings on the facets, either in the form of a radial pattern 4,14,26 , or as a slip-like pattern in a Ti-22V-4Al alloy. 28 In this case, the markings are not radial, but instead are more linear, which suggests that they could be slip traces. However, some of the nano-roughness features deviate from the linear pattern, as can be seen for example in Figure 6.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…3,10,13,26 On the other hand, several publications report that dislocation slip occurs in the α grain and leads to a facet under certain conditions. 7,11,14,21,23,25,[27][28][29][30][31] Even twinning has been suggested to be at the basis of facet formation. 8 It is also important to take into account the fact that the environment for an internal crack will be different compared to a surface crack.…”

Section: Introductionmentioning

confidence: 99%

“…3,7,8,10,11,13,17,20,25 However, a few publications mention the presence of a radial pattern within one facet, 4,14,26 and slip-like patterns have been noticed on facets in a Ti-22V-4Al alloy. 28 Furthermore, fatigue testing using a spike loaded spectrum can lead to markings on facets. 21 Since all of the current research on facets in internal fatigue crack initiation is limited to testing on forged plates or rods, the main objective of this study is to investigate this phenomenon in drawn Ti-6Al-4V wire.…”

Section: Introductionmentioning

confidence: 99%

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Internal fatigue crack initiation in drawn Ti–6Al–4V wires

Everaerts

Verlinden

Wevers

2016

Materials Science and Technology

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Fatigue cracks in titanium alloys are often found to initiate at faceted alpha grains. In the very high cycle fatigue regime, crack initiation tends to shift from the surface towards the interior of the material, and more initiation facets can be found on the fracture surface. In this study, fatigue tests were performed on drawn and heat-treated Ti-6Al-4V wires. Only a few samples fractured due to interior initiation. The facets at the initiation sites of these samples were not flat, but had markings on the nano-scale, and were highly inclined. A possible explanation for these aspects is the crystallographic texture of the wire, and a reflection is made on the suggested mechanisms of facet formation.

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Subsurface fatigue crack initiation in beta titanium alloys

Cited by 28 publications

References 10 publications

Formation of Grain Boundary α in β Ti Alloys: Its Role in Deformation and Fracture Behavior of These Alloys

Formation of Grain Boundary α in β Ti Alloys: Its Role in Deformation and Fracture Behavior of These Alloys

Fracture Surface Facets and Fatigue Life Potential of Castings

Internal fatigue crack initiation in drawn Ti–6Al–4V wires

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