Deformation of polysynthetically twinned crystals of TiAl with a nearly stoichiometric composition

Fujiwara, Toshiaki; Nakamura, Ayako; Hosomi, Masanori; Nishitani, Shigeto R.; Shirai, Yoshihito; Yamaguchi, M.

doi:10.1080/01418619008231937

Cited by 297 publications

(76 citation statements)

References 19 publications

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“…Throughout the 1990s and 2000s, there was a considerable drive to develop compositions and processing methods that resulted in texturefree microstructures [117], where a growing fatigue crack is therefore likely to encounter all possible colony Figure 12. (a) Yield stress of PST specimens as a function of the angle at which the compression axis is inclined to the lamellar planes, from [9], using data from Fujiwara et al [119] (black circles) and Nomura et al [120] (white circles). (b) Dependence of the fatigue threshold on the lamellar orientation, , of the colony where the crack is propagating, from [118] (reproduced with permission).…”

Section: Fatigue Cracking Of Specific Colony Orientations In Polycrysmentioning

confidence: 99%

Recent progress in the high-cycle fatigue behaviour of γ-TiAl alloys

Edwards

2018

Materials Science and Technology

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The high-cycle fatigue (HCF) properties of γ -TiAl (gamma titanium aluminide) alloys are reviewed, particularly with regards to the deformation mechanisms active in the near-threshold cyclic loading regime. By examining the influence of lamellar orientation and thickness on the HCF threshold, in addition to more conventional microstructural considerations such as the grain size or the volume fraction of lamellar colonies, factors to improve the γ -TiAl microstructure for HCF are assessed. Finally, experimental methods and loading strategies are surveyed to identify techniques for improving HCF testing of γ -TiAl alloys. In this, we consider both the conservativism of differing approaches and the possibility to measure with suitable resolution the local mechanical behaviour under HCF of the lamellar γ -TiAl microstructure. ARTICLE HISTORY

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Section: Fatigue Cracking Of Specific Colony Orientations In Polycrysmentioning

confidence: 99%

Recent progress in the high-cycle fatigue behaviour of γ-TiAl alloys

Edwards

2018

Materials Science and Technology

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“…The thermal conductivity of binary compounds with the crystal structures of B2, L1 2 , D0 3 , D0 19 , etc. are summarized as a function of composition, constituent and temperature in this chapter.…”

Section: Thermal Conductivity Of Binary Intermetallic Compoundsmentioning

confidence: 99%

“…[1][2][3][4][5][6][7] Extensive research works have focused on developing the advanced aerospace structure and propulsion systems. Those candidates are mostly the compounds with metallic bonding such as NiAl, [8][9][10] Ni 3 Al [11][12][13][14][15][16] and TiAl [17][18][19][20][21][22][23] due to the combination of high melting temperature, low density and excellent corrosion resistance. Despite their brittleness at low temperatures, they provide an ideal basis for further development as high-temperature structural materials.…”

Section: Introductionmentioning

confidence: 99%

Thermal Conductivity of Intermetallic Compounds with Metallic Bonding

et al. 2002

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Thermal conductivity is one of the key parameters required for high-temperature structural applications of metallic materials. In this overview, the thermal conductivity of intermetallic compounds are extensively described based mainly on our past works, since there had been less works in this research field. Emphasis is placed on the B2 and the L1 2 compounds with metallic bonding such as NiAl, Ni 3 Al, etc., which have been attracting attention for engineering applications at higher temperatures. The thermal conductivity data have been accumulated for the intermetallic compounds, and the phenomenological aspects are reviewed in detail as a function of alloy composition, constituent and temperature. The Wiedemann-Franz law is applicable to the intermetallic compounds, indicating that the carrier of thermal conduction is an electron rather than a phonon. The thermal conductivity of an intermetallic compound with the ordered crystal structure is characterized as an enhancement due to ordering with reference to the basic contribution of solid solution with the disordered crystal structure. It is demonstrated that the thermal conductivity of intermetallic compounds is reduced by the addition of a third element, and this subject is also covered.

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“…As a result, there are six possible ways to fulfill the crystallographic relationships between the two phases, and thus, the γ phase is ordered as six domains in each γ lamella. This special structure leads to a markedly anisotropic deformation behavior [3][4][5]. When the loading axis is parallel (A orientation) or perpendicular (N orientation) to the lamellar boundaries, the material is plastically hard, but when the loading axis is inclined to the lamellar boundaries, it is relatively soft.…”

Section: Introductionmentioning

confidence: 99%

“…The deformation behavior of this material also has attracted a a great deal of attention, but it is difficult to study the deformation mechanisms in random polycrystals due to the complexity of the interfaces. Polysynthetically twinned (PST) crystals, on the other hand, are especially good candidates for studying the interaction of slip and twinning systems with boundaries [3][4][5] because the lamellar boundaries appear to dramatically control the gross deformation behavior of the crystal.…”

Section: Introductionmentioning

confidence: 99%

Dislocation/Twin/Interface Interactions during Deformation of PST TiAl Single Crystals, an AFM Study

2002

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PST TiAl crystals oriented such that the deformation axis lies in the (111) interfacial planes have been deformed in compression. This deformation produces so-called "channeled flow" in which the strain perpendicular to the (111) interfaces is zero, while the other two strains are equal and opposite in sign. Thus the sample simply shortens axially and spreads laterally in the channels defined by the (111) interfacial planes. We have examined the fine structure of deformation bands on the free surface of these deformed samples using AFM to see how the deformation processes interact with the boundaries. By measuring the offset angle at the surface we have been able to show that not only is the macroscopic displacement vector parallel to the lamellar boundaries, but the total shear vector in each layer is also parallel to the lamellar boundaries. However these deformation bands have very different characters, requiring complex deformation processes at the boundaries in order to satisfy this requirement. Some consist of either just super dislocations or just ordinary dislocations with Burgers vectors lying in the interface. But others consist of a special combination of twinning and ordinary dislocations in fixed ratio, such that the net shear vector also lies in the boundary, even though the individual twinning and dislocation shear directions are inclined to it. This results in deformation that is homogeneous and completely 'channeled' inside each lamella with no shear vector perpendicular to the lamellar boundaries. We have also shown that the cooperative twinning and slip is homogeneous on the nanoscale, i.e., the twinning and slip occurs in the same volume of material. (111) interfacial planes have been deformed in compression. This deformation produces so-called "channeled flow" in which the strain perpendicular to the (111) interfaces is zero, while the other two strains are equal and opposite in sign. Thus the sample simply shortens axially and spreads laterally in the channels defined by the (111) interfacial planes. We have examined the fine structure of deformation bands on the free surface of these deformed samples using AFM to see how the deformation processes interact with the boundaries. By measuring the offset angle at the surface we have been able to show that not only is the macroscopic displacement vector parallel to the lamellar boundaries, but the total shear vector in each layer is also parallel to the lamellar boundaries. However these deformation bands have very different characters, requiring complex deformation processes at the boundaries in order to satisfy this requirement. Some consist of either just super dislocations or just ordinary dislocations with Burgers vectors lying in the interface. But others consist of a special combination of twinning and ordinary dislocations in fixed ratio, such that the net shear vector also lies in the boundary, even though the individual twinning and dislocation shear directions are inclined to it. This results in deformation that is homogeneou...

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Deformation of polysynthetically twinned crystals of TiAl with a nearly stoichiometric composition

Cited by 297 publications

References 19 publications

Recent progress in the high-cycle fatigue behaviour of γ-TiAl alloys

Recent progress in the high-cycle fatigue behaviour of γ-TiAl alloys

Thermal Conductivity of Intermetallic Compounds with Metallic Bonding

Dislocation/Twin/Interface Interactions during Deformation of PST TiAl Single Crystals, an AFM Study

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