Mechanisms of Ti<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si9.svg"><mml:msub><mml:mrow/><mml:mn>3</mml:mn></mml:msub></mml:math>Al precipitation in hcp <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:mi>α</mml:mi></mml:math>-Ti

Dear, Felicity F.; Kontis, Paraskevas; Gault, Baptiste; Ilavský, Ján; Rugg, David; Dye, David

doi:10.1016/j.actamat.2021.116811

Cited by 28 publications

(9 citation statements)

References 38 publications

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“…More recent experimental efforts reported by Gardner et al confirms the encouragement of α 2 formation from oxygen addition and oxygen partitioning [31][32][33] . Furthermore, a similar conclusion has also been made in a more comprehensive investigation about the effect of solution species (including O, Mo, and V) on Ti 3 Al precipitation in hcp α-Ti by Dear et al 34 .…”

Section: Discussionsupporting

confidence: 71%

Elimination of oxygen sensitivity in α-titanium by substitutional alloying with Al

et al. 2021

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Individually, increasing the concentration of either oxygen or aluminum has a deleterious effect on the ductility of titanium alloys. For example, extremely small amounts of interstitial oxygen can severely deteriorate the tensile ductility of titanium, particularly at cryogenic temperatures. Likewise, substitutional aluminum will decrease the ductility of titanium at low-oxygen concentrations. Here, we demonstrate that, counter-intuitively, significant additions of both Al and O substantially improves both strength and ductility, with a 6-fold increase in ductility for a Ti-6Al-0.3 O alloy as compared to a Ti-0.3 O alloy. The Al and O solutes act together to increase and sustain a high strain-hardening rate by modifying the planar slip that predominates into a delocalized, three-dimensional dislocation pattern. The mechanism can be attributed to decreasing stacking fault energy by Al, modification of the “shuffle” mechanism of oxygen-dislocation interaction by the repulsive Al-O interaction in Ti, and micro-segregation of Al and O by the same cause.

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Section: Discussionsupporting

confidence: 71%

Elimination of oxygen sensitivity in α-titanium by substitutional alloying with Al

et al. 2021

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“…Thus, the L-PBF process allows reaching the precipitation temperature range for a sufficient time to form α 2 precipitates. In fact, some authors showed that α 2 precipitates in the range of 500–600 °C for several hours [ 222 , 241 , 251 ]. Dear et al [ 251 ], considering the as-cast Ti-7Al, showed an increase in the intensity of superlattice reflections of α 2 -Ti 3 Al through TEM micrographs after 500 °C × 2 h (AC).…”

Section: L-pbfed Ti6al4v: Microstructurementioning

confidence: 99%

“…In fact, some authors showed that α 2 precipitates in the range of 500–600 °C for several hours [ 222 , 241 , 251 ]. Dear et al [ 251 ], considering the as-cast Ti-7Al, showed an increase in the intensity of superlattice reflections of α 2 -Ti 3 Al through TEM micrographs after 500 °C × 2 h (AC). The intensity increases significantly after 240 and 2880 h. In this scenario, not only the thermal gradient reached during the L-PBF process but also the Al and O contents promote the α 2 transformation due to their effects on the α + α 2 phase-field [ 252 , 253 ].…”

Section: L-pbfed Ti6al4v: Microstructurementioning

confidence: 99%

Additive Manufacturing of AlSi10Mg and Ti6Al4V Lightweight Alloys via Laser Powder Bed Fusion: A Review of Heat Treatments Effects

Ghio

Cerri

2022

Materials

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Laser powder bed fusion (L-PBF) is an additive manufacturing technology that is gaining increasing interest in aerospace, automotive and biomedical applications due to the possibility of processing lightweight alloys such as AlSi10Mg and Ti6Al4V. Both these alloys have microstructures and mechanical properties that are strictly related to the type of heat treatment applied after the L-PBF process. The present review aimed to summarize the state of the art in terms of the microstructural morphology and consequent mechanical performance of these materials after different heat treatments. While optimization of the post-process heat treatment is key to obtaining excellent mechanical properties, the first requirement is to manufacture high quality and fully dense samples. Therefore, effects induced by the L-PBF process parameters and build platform temperatures were also summarized. In addition, effects induced by stress relief, annealing, solution, artificial and direct aging, hot isostatic pressing, and mixed heat treatments were reviewed for AlSi10Mg and Ti6AlV samples, highlighting variations in microstructure and corrosion resistance and consequent fracture mechanisms.

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“…In the aged high-oyxgen alloy, the restriction of dislocations to slip bands is even more severe. We suggest this is due to the higher strength of the surrounding unslipped material, due to refinement of α 2 by raised O content [25]. This increases the difficulty of setting up new slip bands, and of dislocation motion outside bands.…”

Section: Resultsmentioning

confidence: 91%

“…c Ageing to precipitate ordered α 2 causes more restricted slip bands, with less crossslip possible due to the formation of antiphase boundaries between leading and trailing dislocations passing through ordered precipitates. d In the high-oxygen alloy, the α 2 dispersion is refined [25], causing even more severe slip banding.…”

Section: Resultsmentioning

confidence: 99%

Dwell fatigue in titanium and the connection between slip intermittency and alloying

F.¹,

Xu²,

Lim³

et al. 2022

Preprint

Self Cite

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Dwell fatigue, the reduction in fatigue life experienced by titanium alloys due to holds at stresses as low as 60% of yield, has been implicated in several uncontained jet engine failures. Dislocation slip has long been observed to be an intermittent, scalebridging phenomenon, similar to that seen in earthquakes but at the nanoscale, leading to the speculation that large stress bursts might promote the initial opening of a crack. Here we observe such stress bursts at the scale of individual grains in situ, using high energy X-ray diffraction microscopy and discrete dislocation plasticity modelling in Ti-7Al-O alloys. This shows that the detrimental effect of precipitation of ordered Ti 3 Al is to increase the magnitude of rare pri a and bas a slip bursts associated with slip localisation. By contrast, the addition of trace O interstitials is beneficial, reducing the magnitude of slip bursts and promoting a higher frequency of smaller events. This is further evidence that the formation of long paths for easy basal plane slip localisation should be avoided when engineering titanium alloys against dwell fatigue.

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Mechanisms of Ti3Al precipitation in hcp α-Ti

Cited by 28 publications

References 38 publications

Elimination of oxygen sensitivity in α-titanium by substitutional alloying with Al

Elimination of oxygen sensitivity in α-titanium by substitutional alloying with Al

Additive Manufacturing of AlSi10Mg and Ti6Al4V Lightweight Alloys via Laser Powder Bed Fusion: A Review of Heat Treatments Effects

Dwell fatigue in titanium and the connection between slip intermittency and alloying

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