Gamma titanium aluminides as prospective structural materials

Loria, Edward A.

doi:10.1016/s0966-9795(00)00073-x

Cited by 356 publications

(146 citation statements)

References 3 publications

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“…In lamellar TiAl-based alloys, whether in polycrystalline form or as polysynthetically twinned single crystals (Fujiwara et al 1990), there are three variants of the twin-related g-g interfaces (Feng et al 1988, Schwartz and Sastry 1989, Inui et al 1992a,b, Yamaguchi et al 1996, 2000. They are Furthermore, the ordered twin with additional APB was observed (Ricolleau et al 1994) and studied in details employing high-resolution electron microscopy and the ab-initio FP LMTO method by Siegl et al 1997.…”

Section: Energies Of Lamellar Interfacesmentioning

confidence: 99%

“…Common negative characteristics of these materials are their small or even non-existent ductility at ambient temperatures. In this respect, the most promising hightemperature intermetallics are titanium aluminides based on g-TiAl with the tetragonal L1 0 structure (Kim 1998, Dimiduk 1998, 1999, Tetsui 1999, Yamaguchi et al 2000, Loria 2000, 2001). These alloys display dramatically different microstructures for different compositions near the 50 : 50 aluminium : titanium ratio (McCullough et al 1988, Froes and Suryanarayama 1996, Zhang et al 1997.…”

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confidence: 99%

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Atomistic modelling of TiAl I. Bond-order potentials with environmental dependence

Znám

Nguyen-Manh

Pettifor

et al. 2003

Philosophical Magazine

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Bond-order potentials (BOPs) for L1 0 TiAl have been developed and constructed within a tight-binding framework. In addition to the usual attractive bond-energy contribution arising from the formation of covalent bonds and pairwise contribution describing the overlap repulsion and electrostatic interaction, we have included an environmentally dependent term to represent the strong repulsion experienced by the valence sp electrons in transition metals and their alloys. The latter contribution is crucial for reproducing the negative Cauchy pressures of TiAl and other transition-metalbased intermetallic compounds. The constructed BOPs have been tested in the following ways: firstly, examination of the mechanical stability of the tetragonal L1 0 lattice with respect to large deformations and other crystal structures with the same stoichiometry; secondly, calculation of the surface for f111g planes and related evaluation of the energies of stacking-fault-type defects; thirdly, calculation of energies of the -interfaces that are present in the lamellar TiAl and energies associated with the formations of point defects in TiAl. The results of all these calculations show very good agreement with various ab-initio calculations. Importantly, we find that this potential is transferable to the different bonding environment in the hexagonal D0 19 Ti 3 Al. Hence these BOPs are suitable for atomistic study of dislocations and other extended defects not only in L1 0 TiAl but also in Ti 3 Al and possibly structures with other titanium-rich stoichiometries.

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Section: Energies Of Lamellar Interfacesmentioning

confidence: 99%

mentioning

confidence: 99%

Atomistic modelling of TiAl I. Bond-order potentials with environmental dependence

Znám

Nguyen-Manh

Pettifor

et al. 2003

Philosophical Magazine

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“…Among these alloys, two phase γ-based TiAl alloys are advancing towards implementation on structural components of aircraft, space and automobile engines [1][2][3][4]. The use of γ-TiAl alloys as structural materials, will require the development of reliable and cost-effective joining techniques.…”

Section: Introductionmentioning

confidence: 99%

Joining Ti-47Al-2Cr-2Nb with a Ti-Ni Braze Alloy

Guedes

Pinto

Vieira

et al. 2004

MSF

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Abstract. Ti-47Al-2Cr-2Nb was joined by diffusion brazing using a Ti-Ni clad-laminated filler alloy. Brazing was performed in the temperature range of 1000 to 1200ºC for 10 min. The microstructure and the chemical composition of the interfaces were studied by scanning electron microscopy (SEM) and by energy dispersive X-ray spectroscopy (EDS), respectively. The reaction between the γ-TiAl alloy and the liquid produced interfaces essentially composed of α 2 -Ti 3 Al and TiNiAl intermetallics. When joints are brazed at 1150 and 1200ºC, the γ-TiAl phase is also detected at the interface.

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“…They present exceptional creep and oxidation resistance along with low density compared with nickel-based and cobalt-based superalloys. [1,2] In particular, TiAl-based intermetallics are targeted for high-temperature aerospace applications in low-pressure turbines (LPTs) because they can provide increased thrust-to-weight ratios and improved efficiency. LPT materials operate in aggressive environments at temperatures up to 1023 K (750°C), and TiAl intermetallics are projected to replace the heavier nickelbased superalloys being used currently for such applications.…”

Section: Introductionmentioning

confidence: 99%

In Situ Observations of the Deformation Behavior and Fracture Mechanisms of Ti-45Al-2Nb-2Mn + 0.8 vol pct TiB2

Muñoz‐Moreno

Boehlert

Pérez‐Prado

et al. 2011

Metall Mater Trans A

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The deformation and fracture mechanisms of a nearly lamellar Ti-45Al-2Nb-2Mn (at. pct) + 0.8 vol pct TiB 2 intermetallic, processed into an actual low-pressure turbine blade, were examined by means of in situ tensile and tensile-creep experiments performed inside a scanning electron microscope (SEM). Low elongation-to-failure and brittle fracture were observed at room temperature, while the larger elongations-to-failure at high temperature facilitated the observation of the onset and propagation of damage. It was found that the dominant damage mechanisms at high temperature depended on the applied stress level. Interlamellar cracking was observed only above 390 MPa, which suggests that there is a threshold below which this mechanism is inhibited. Failure during creep tests at 250 MPa was controlled by intercolony cracking. The in situ observations demonstrated that the colony boundaries are damage nucleation and propagation sites during tensile creep, and they seem to be the weakest link in the microstructure for the tertiary creep stage. Therefore, it is proposed that interlamellar areas are critical zones for fracture at higher stresses, whereas lower stress, high-temperature creep conditions lead to intercolony cracking and fracture.

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Gamma titanium aluminides as prospective structural materials

Cited by 356 publications

References 3 publications

Atomistic modelling of TiAl I. Bond-order potentials with environmental dependence

Atomistic modelling of TiAl I. Bond-order potentials with environmental dependence

Joining Ti-47Al-2Cr-2Nb with a Ti-Ni Braze Alloy

In Situ Observations of the Deformation Behavior and Fracture Mechanisms of Ti-45Al-2Nb-2Mn + 0.8 vol pct TiB2

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