Silicide precipitation strengthened TiAl

Noda, Toshiharu; Okabe, Masaru; Isobe, Susumu; Sayashi, Mamoru

doi:10.1016/0921-5093(94)03313-7

Cited by 92 publications

(45 citation statements)

References 9 publications

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“…Theses results differ from those in the literatures. The literatures show that the precipitated particles clearly reduce the minimum creep rate as compared to its mother alloy in the stress range from 200 to 300 MPa at 1073 K. 12,13) The difference is owing to that in this study most of the creep responses are dominated by the tertiary creep. The Sc addition has no effect on both the primary and secondary creep.…”

Section: Creep Behaviormentioning

confidence: 58%

“…The literature demonstrates that adding a small amount of Si, N, or C improves creep resistance by impeding of particles to dislocation motion. [12][13][14] Base on the strengthening effects of precipitates at high temperature, the Ti-40Al-16Nb alloy with the addition of a little of a quaternary element, such as Sc, is used to elucidate the properties of the specified alloy at high temperature. Accordingly, the object of this study is to investigate the creep behavior of Ti-40Al-16Nb alloy, with high Nb content, as well as the precipitation hardening by a small amount of Sc element added.…”

Section: Introductionmentioning

confidence: 99%

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Creep Behavior of Ti–40Al–16Nb Intermetallic Alloy and Strengthening Effects of Minor Sc

Zhan

Koo

2006

Mater. Trans.

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The creep behavior of the Ti-40Al-16Nb alloy and the effect of the minor addition of Sc are investigated by creep tests at 1073 K under constant load from 200 to 280 MPa. The creep curve of the alloy with high Nb contents does not exhibit a steady-state region, and the minor addition of Sc added to the alloy has no effect on minimum creep rate. The creep responses of the alloys with high Nb contents are strongly correlated with tertiary creep behavior. The effects of Sc addition are apparent on the properties of tertiary creep rate and rupture life. The tertiary creep rate of the Sc containing alloy is reduced and the creep fracture life is increased. Subgrain structures of dislocations are absent in the alloys with high Nb contents during secondary creep, and the deformation of creep converges mainly at the B2 phase. A stress exponent of 4.5 estimated indicates that the mechanism of controlling creep behavior is dislocation climb. The creep fracture of the alloys is dominated by cleavage fracture over the entire fracture surface. Sc 2 O 3 particles are an effective obstacle to the propagation of cracks and the motion of dislocations.

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Section: Creep Behaviormentioning

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Creep Behavior of Ti–40Al–16Nb Intermetallic Alloy and Strengthening Effects of Minor Sc

Zhan

Koo

2006

Mater. Trans.

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“…[26] The improvement in creep properties has been attributed to pinning of dislocations by the titanium silicide particles or to the stabilization of the lamellar boundaries, so as to inhibit dynamic recrystallization. [26,27] To our knowledge, little work concerning the effects of Si additions on the properties of Ti 3 Al-based alloys with (␣ 2 ϩ B2 ϩ O) microstructures has been reported. The objective of the present study is to incorporate a small fraction of the Ti 5 Si 3 phase into a Ti-24Al-14Nb-3V-0.5Mo alloy, with a view to improving its comprehensive properties.…”

Section: Introductionmentioning

confidence: 98%

A comparison study of microstructure and mechanical properties of Ti-24Al-14Nb-3V-0.5Mo with and without Si

Lü

Yang

Cui

et al. 2000

Metall Mater Trans A

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A comparative study has been made of the room-and elevated-temperature tensile properties, roomtemperature fracture toughness, fatigue-crack propagation rates, and 650 ЊC creep properties of Ti24Al-14Nb-3V-0.5Mo with and without 0.9 at. pct Si. Both alloys have microstructures consisting of the ␣ 2 , B2, and the orthorhombic O phase, with different proportions of the ␣ 2 phase relative to the (O ϩ B2) mixtures, depending on solution-treatment temperature. The alloy with a Si addition contains additional primary -Ti 5 Si 3 particles distributed in the (O ϩ B2) matrix. Tests of mechanical properties showed that the incorporation of a small fraction (about 0.03 by volume) of the Ti 5 Si 3 phase leads to greater room-temperature and elevated-temperature strengths, but lower room-temperature elongations and fracture toughness as compared with the base alloy. Alloys containing greater volume fractions of the ␣ 2 phase exhibited better tensile ductility, and this was attributed to the concurrent stabilization of the B2 phase. Examination of tensile-tested and fatigued specimens indicates that the primary failure mode of the alloys, regardless of Si addition, was due to the brittleness of the ␣ 2 phase; the silicide particles that debonded from the matrix also contribute to cracking in the monotonic loading mode. Up to a 20 pct improvement in creep-rupture life was observed in the Si-containing alloys, and this was interpreted in terms of the solute-strengthening effect of Si. While the incorporated Ti 5 Si 3 phase has an unfavorable effect on ductility and room-temperature fracture toughness, the difference in fatigue-crack propagation rates between the alloys with and without Si is minimal. It is concluded that the controlling factor for the fatigue failure in orthorhombic alloys is related to the (␣ 2 ϩ O ϩ B2) microstructure, instead of the Ti 5 Si 3 particles.

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“…The mechanism behind the improvement of creep behaviour due to Si addition in near-α alloys is still controversial. Two mechanisms have been suggested: one involves the interaction between Si and dislocations [1,2,3,4,5,6,7]; the second identifies silicides as the reason for a better creep behaviour [8,9]. On the other hand, faster diffusers, such as Fe, Ni, and Co, have negative influence on the creep properties of Ti alloys [7,10,11,12].…”

Section: Introductionmentioning

confidence: 99%

First‐principles investigation of solute diffusion mechanisms in alpha‐Ti

Scotti

Mottura

2016

Proceedings of the 13th World Conference on Titanium

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Different mechanisms such as solidification and precipitation are governed by diffusion mechanisms. For example, it is well known that silicon improves the high temperature properties of alpha-Ti alloys, as a result of the slow Si diffusion. It has also been reported that oxygen and nitrogen have high solubility and high diffusivity in alpha-Ti and they promote the formation of alpha-case, reducing the hightemperature properties of these alloys. In this work, the diffusivity of solute atoms in alpha-Ti is studied in depth. This is done by using the 8-frequency model, the multi-state diffusion method, and kinetic Monte Carlo (all informed by density functional theory) to investigate the characteristics of vacancymediated, interstitial and more complex diffusion processes in alpha-Ti. Initial results indicate that some of the poor metals (Si, Ge) display extreme diffusion anisotropy, while late 3d transition metals (Fe, Co, Ni) display a mixed interstitial-substitutional diffusion process.

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Silicide precipitation strengthened TiAl

Cited by 92 publications

References 9 publications

Creep Behavior of Ti–40Al–16Nb Intermetallic Alloy and Strengthening Effects of Minor Sc

Creep Behavior of Ti–40Al–16Nb Intermetallic Alloy and Strengthening Effects of Minor Sc

A comparison study of microstructure and mechanical properties of Ti-24Al-14Nb-3V-0.5Mo with and without Si

First‐principles investigation of solute diffusion mechanisms in alpha‐Ti

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Silicide precipitation strengthened TiAl

Cited by 92 publications

References 9 publications

Creep Behavior of Ti&ndash;40Al&ndash;16Nb Intermetallic Alloy and Strengthening Effects of Minor Sc

Creep Behavior of Ti&ndash;40Al&ndash;16Nb Intermetallic Alloy and Strengthening Effects of Minor Sc

A comparison study of microstructure and mechanical properties of Ti-24Al-14Nb-3V-0.5Mo with and without Si

First‐principles investigation of solute diffusion mechanisms in alpha‐Ti

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Creep Behavior of Ti–40Al–16Nb Intermetallic Alloy and Strengthening Effects of Minor Sc

Creep Behavior of Ti–40Al–16Nb Intermetallic Alloy and Strengthening Effects of Minor Sc