The role of the ω phase on the non-classical precipitation of the α phase in metastable β-titanium alloys

Zheng, Yufeng; Williams, Robert E.A.; Sosa, J.M.; Wang, Yunzhi; Banerjee, Rajarshi; Fraser, Hamish L.

doi:10.1016/j.scriptamat.2015.08.019

Cited by 99 publications

(41 citation statements)

References 16 publications

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“…Similar observations were recently made in the near-beta Ti-5Al-5Mo-5V-3Cr (wt. %) alloy [135,136] and the near-beta Ti-7Mo-3Nb-3Cr-3Al (wt. %) alloy [137].…”

Section: Agingmentioning

confidence: 99%

A Review of Metastable Beta Titanium Alloys

Kolli

Devaraj

2018

Metals

430

175

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Abstract:In this article, we provide a broad and extensive review of beta titanium alloys. Beta titanium alloys are an important class of alloys that have found use in demanding applications such as aircraft structures and engines, and orthopedic and orthodontic implants. Their high strength, good corrosion resistance, excellent biocompatibility, and ease of fabrication provide significant advantages compared to other high performance alloys. The body-centered cubic (bcc) β-phase is metastable at temperatures below the beta transus temperature, providing these alloys with a wide range of microstructures and mechanical properties through processing and heat treatment. One attribute important for biomedical applications is the ability to adjust the modulus of elasticity through alloying and altering phase volume fractions. Furthermore, since these alloys are metastable, they experience stress-induced transformations in response to deformation. The attributes of these alloys make them the subject of many recent studies. In addition, researchers are pursuing development of new metastable and near-beta Ti alloys for advanced applications. In this article, we review several important topics of these alloys including phase stability, development history, thermo-mechanical processing and heat treatment, and stress-induced transformations. In addition, we address recent developments in new alloys, phase stability, superelasticity, and additive manufacturing.

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“…Similar observations were recently made in the near-beta Ti-5Al-5Mo-5V-3Cr (wt. %) alloy [135,136] and the near-beta Ti-7Mo-3Nb-3Cr-3Al (wt. %) alloy [137].…”

Section: Agingmentioning

confidence: 99%

A Review of Metastable Beta Titanium Alloys

Kolli

Devaraj

2018

Metals

430

175

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“…On the other hand, isothermal ω structure develops after subsequent annealing at a temperature below ω solvus. After prolonged aging, isothermal ω is known to promote α phase either directly by acting as heterogeneous nucleation sites or indirectly [17][18][19][20]. It is known that ω structure is formed due to collapse of {111} planes in β phase [14,15].…”

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confidence: 99%

Influence of oxygen on omega phase stability in the Ti-29Nb-13Ta-4.6Zr alloy

et al. 2016

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“…In our recent studies, coupling atom probe and aberration-corrected scanning transmission electron microscope, several novel phase transformation mechanisms have been systematically explored in a beta titanium alloy, Ti-5Al-5Mo-5V-3Cr (Ti-5553, wt.%) [1][2][3][4]. It has been clearly shown that the size, morphology and number density of hcp structure alpha precipitates in Ti-5553 can be significantly influenced by the nano-scale structural and compositional instability, more specifically the metastable hexagonal structure isothermal omega phase, present in parent bcc structure beta phase.…”

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confidence: 99%

Investigation of Novel Phase Transformation Mechanisms in Titanium Alloys Using Atom Probe and Aberration-Corrected Scanning Transmission Electron Microscope

et al. 2017

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Metastable beta titanium alloys have attracted significant amount of attentions in recent years, because their microstructures can be manipulated by different phase transformation mechanisms and therefore the corresponding mechanical properties vary significantly by adopting various thermal/mechanical processes. In our recent studies, coupling atom probe and aberration-corrected scanning transmission electron microscope, several novel phase transformation mechanisms have been systematically explored in a beta titanium alloy, Ti-5Al-5Mo-5V-3Cr (Ti-5553, wt.%) [1][2][3][4]. It has been clearly shown that the size, morphology and number density of hcp structure alpha precipitates in Ti-5553 can be significantly influenced by the nano-scale structural and compositional instability, more specifically the metastable hexagonal structure isothermal omega phase, present in parent bcc structure beta phase. Computational simulation has shown that the compositional and/or stress field associated with such nano-scale instabilities may contribute to an increased driving force for alpha nucleation [3,5,6]. In order to provide accurate input into computational simulation, the compositional and structural insights of nanoscale instabilities in parent phase matrix are highly demanded in experiment. Such detailed characterization is relied on the recent technological improvement in atom probe and TEM that has the potential to provide atomic resolution information in titanium alloys.In the first part of this current work, nano-scale omega phase particles in Ti-5553 were investigated using atom probe (LEAP 3000X HR) and probe corrected scanning transmission electron microscope (FEI Titan™ 80-300) [3]. For the first time, using atom probe, the elliptical morphology isothermal omega phase particles of nano-scale are clearly observed and the concentration of omega phase is characterized that both alpha phase stabilizer, Al, and beta phase stabilizers, V, Mo, and Cr, are rejected from omega phase into beta phase matrix, shown in Fig. 1(a). The structure of omega phase is characterized using Z-contrast HAADF-STEM imaging, that every two of three adjacent {111} atom planes are observed to collapsed leaving the third atom plane unaltered, as shown in Fig 1(b).The second part of the work to be presented focused on the characterization of omega phase assisted alpha precipitation in another beta titanium alloy, . For the first time, conclusive experimental evidence of nucleation of alpha precipitates at the omega/beta interface was obtained using atom probe (LEAP 3000X HR) and probe corrected scanning transmission electron microscope (FEI Titan™ 80-300), as shown in Fig. 2. HAADF-STEM image in Fig. 2(a) shows the clear contact of hcp structure alpha precipitate with pre-formed hexagonal structure isothermal omega particle, which is further validated using atom probe shown in Fig. 2(b) that alpha precipitate is formed at the pre-formed interface between coarse cuboidal morphology omega particle and beta matrix in three dimensions with a simila...

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The role of the ω phase on the non-classical precipitation of the α phase in metastable β-titanium alloys

Cited by 99 publications

References 16 publications

A Review of Metastable Beta Titanium Alloys

A Review of Metastable Beta Titanium Alloys

Influence of oxygen on omega phase stability in the Ti-29Nb-13Ta-4.6Zr alloy

Investigation of Novel Phase Transformation Mechanisms in Titanium Alloys Using Atom Probe and Aberration-Corrected Scanning Transmission Electron Microscope

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