Mechanical behavior of submicron-grained γ-TiAl-based alloys at elevated temperatures

Bohn, Rainer; Klassen, Thomas; Bormann, R.

doi:10.1016/s0966-9795(01)00039-5

Cited by 60 publications

(32 citation statements)

References 33 publications

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“…The activation energy for creep lies between that of Ti and Al self-diffusion in TiAl (2.59 eV and 3.71 eV) [16]. Similar conclusions have been drawn by [17][18][19][20][21]. On the other hand, in the coarsegrained sample A before DRX, creep is dominated by dislocation climb with a stress exponent of 4.2 [22].…”

Section: Resultssupporting

confidence: 75%

High strain torsion of a TiAl-based alloy

Cao

Klöden

Rybacki

et al. 2008

Materials Science and Engineering: A

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A two-phase lamellar and globular TiAl-based alloy Nb, Ta, B)) with different textures has been deformed in torsion in a Paterson-type rock deformation machine at a temperature of 1173 K under 400 MPa argon confining pressure. The shear stress -shear strain curves with increasing shear strain show a decrease or increase of shear stress in the lamellar and globular case, respectively, to a common steady state value. Activation analysis at high strains yields stress exponents of about 1.8 and an activation energy of 3.29 eV. With increasing shear strain the lamellar structure breaks down and a two-phase fine-grained globular structure develops by recrystallization with a grain size in the order of 2 microns. The weak initial fibre textures at high strains are randomized. The mechanical, microstructural and textural features indicate a transition from dislocation creep to superplastic flow.

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Section: Resultssupporting

confidence: 75%

High strain torsion of a TiAl-based alloy

Cao

Klöden

Rybacki

et al. 2008

Materials Science and Engineering: A

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“…It has been observed that the pores size slightly increased as the testing temperature increased. This behaviour is similar to that observed in other studies [14,22]. It can be understood that cavities formed during elevated temperature tensile testing is due to four reasons: a) residual pores; b) improper accommodation of the shear strains; c) thermally induced pores (TIP) due to entrapped gas inside the bulk material; and d) separation of particles at interparticle boundaries without bonding.…”

Section: Elevated Temperature Mechanical Behavioursupporting

confidence: 88%

“…The observation that the yield stresses of TiAl based alloys at temperatures above 800 o C are lower as compared to those of their coarse grained counterparts at the same temperatures is in agreement with the observation made by Yan et al [20]. According to Bohn et al [14] and Oehring et al [15,21] the mechanisms of creep of TiAl based alloys at elevated temperatures are dislocation climb and grain boundary sliding (GBS) facilitated by atomic diffusion. Grain boundary sliding is expected to occur above 1000 o C for coarse grained TiAl based alloys, while this mechanism can be one of the dominant mechanisms of creep at temperatures well below 1000 o C for UFG TiAl alloys.…”

Section: Elevated Temperature Mechanical Behavioursupporting

confidence: 87%

“…While in compression the samples showed yielding with an average yield strength of 1410MPa which is comparable to that of UFG -TiAl alloys with similar compositions and grain sizes [14] and significantly higher than that of coarse grained -TiAl alloys with similar compositions [13]. However Oehring et.…”

Section: Room Temperature Mechanical Behaviourmentioning

confidence: 76%

“…However for the alloys prepared in ideal conditions and with no microstructural defects only two types of cavitation behaviour may be expected, which can be either from TIP or improper accommodation of sliding strain. Also it is known fact that reducing the grain size is used as a counter measure to reduce cavitation [14,22], so the increase in pore size observed in the Ti-47Al-2Cr alloy with the grains at UFG level can be mainly attributed to the residual pores and opening up of non bonded interparticle boundaries.…”

Section: Elevated Temperature Mechanical Behaviourmentioning

confidence: 99%

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The mechanical behaviour of an ultrafine grained Ti–47Al–2Cr (at%) alloy in tension and compression and at different temperatures

Nadakuduru

Zhang

Cao

et al. 2011

Materials Science and Engineering: A

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A c c e p t e d M a n u s c r i p t Research Highlights Powder metallurgy process has been used to produce UFG Ti-47Al-2Cr (at%) alloy. At room temperature, the UFG alloy was found to be ductile in compression (~ 4%). At elevated temperatures the alloy showed high tensile and compressive ductility. The yield strength at 900 o C is 55MPa in tension and ~ 33MPa in compression. *Research HighlightsPage 2 of 17 A c c e p t e d M a n u s c r i p t AbstractA bulk ultrafine grained (UFG) Ti-47Al-2Cr (at%) alloy has been produced using a powder metallurgy process that combines high energy mechanical milling (HEMM) of a mixture of Ti, Al and Cr powders to produce a Ti/Al/Cr composite powder and hot isostatic pressing (HIP) of the composite powder compact. The purpose of the present study is to determine the mechanical behaviour of the alloy in tension and compression at room temperature (RT) and elevated temperatures, and also to compare the compression behaviour of the material with its tensile behaviour. It has been found that due to the residual pores, lack of full level interparticle bonding and high oxygen content (0.87wt%) in the consolidated samples, the UFG TiAl based alloy has a very low room temperature tensile fracture strength of ~100MPa and shows no tensile ductility. However these microstructural defects and high oxygen content have much less significant effect on the room temperature compressive mechanical properties, and the alloy shows a high compressive yield strength of ~ 1410 MPa, and some ductility (plastic strain to fracture ~ 4%). At elevated temperatures of 800 o C and above, the alloy shows high tensile and compressive ductility as demonstrated by 75% tensile elongation to fracture and no cracking in upset forging with a height reduction of 50% at 900 o C. The yield strength of the alloy at 900 o C is 55MPa in tension and ~ 33MPa in compression, both of which are lower than those of coarse grained TiAl based alloys with similar compositions at 900 o C. This is due to a higher creep rate of the UFG alloy caused by the small grains. The good formability of the UFG TiAl based alloy as reflected by the lower critical temperature above which the alloy becomes highly formable indicates that the material can be used as a suitable precursor for secondary thermomechanical processing and super-plastic forming.

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Powder Metallurgy

2011

Gamma Titanium Aluminide Alloys

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Mechanical behavior of submicron-grained γ-TiAl-based alloys at elevated temperatures

Cited by 60 publications

References 33 publications

High strain torsion of a TiAl-based alloy

High strain torsion of a TiAl-based alloy

The mechanical behaviour of an ultrafine grained Ti–47Al–2Cr (at%) alloy in tension and compression and at different temperatures

Powder Metallurgy

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