Dislocations observed by transmission electron microscopy in the quasicrystalline phase T2 of Al-Li-Cu after deformation

Yu, Dapeng; Staiger, W.; Kléman, M.

doi:10.1080/09500839208207535

Cited by 14 publications

(3 citation statements)

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“…It contains an icosahedral phase of F-type lattice structure, of which single quasicrystals can be grown by the Czochralski technique [2,3]. After the first observation of lattice defects in the form of dislocations in decagonal AI65CU20C015 and icosahedral Al65Cu2oFei5, similar observations were reported for other stable quasicrystalline phases [4][5][6][7][8][9]. These observations raised the question of the origin of the dislocations, in particular, whether they can be induced by plastic deformation.…”

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confidence: 63%

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Direct evidence for plastic deformation of quasicrystals by means of a dislocation mechanism

et al. 1993

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Single quasicrystals of Al?oPd2iMn9 were plastically deformed by 25% under compression at 750°C. Both these samples as well as control samples of as-grown and heat-treated material were investigated by transmission electron microscopy. It was found that upon deformation the dislocation density increases by about 2 orders of magnitude. This provides the first direct evidence for quasicrystal deformation by a dislocation mechanism. The dislocations were found to have twofold and fivefold Burgers vector directions in physical space.PACS numbers: 61.44.+p, 6L66.Dk, 61.72.Bb, 62.20.Fe In a number of ternary aluminum-transition metal alloy systems thermodynamically stable quasicrystalline phases occur which can be produced with high structural perfection [l]. Of these alloys Al-Pd-Mn is particularly attractive. It contains an icosahedral phase of F-type lattice structure, of which single quasicrystals can be grown by the Czochralski technique [2,3]. After the first observation of lattice defects in the form of dislocations in decagonal AI65CU20C015 and icosahedral Al65Cu2oFei5, similar observations were reported for other stable quasicrystalline phases [4][5][6][7][8][9]. These observations raised the question of the origin of the dislocations, in particular, whether they can be induced by plastic deformation. Indeed hardness and compression tests demonstrated a relatively high ductility which increases with temperature [10][11][12][13][14][15]. With the exception of a hardness test at room temperature [10], these studies were all carried out in polyquasicrystalline material. We are reporting here on the first high-temperature single quasicrystal deformation experiments. Transmission electron microscopy of deformed and undeformed single quasicrystals of Al7 0 Pd2r Mn9 indicates an increase in dislocation density by about 2 orders of magnitude after plastic deformation, providing the first direct evidence for quasicrystal deformation by a dislocation mechanism.A master alloy of composition Al7 0 Pd2iMn9 was prepared in an induction furnace under an Ar atmosphere. Employing the Czochralski technique the resulting ingot was used to grow a single quasicrystal 7 cm in length and 1 cm in diameter of [0/0,0/0,0/2] orientation (notation of Cahn, Schechtman, and Gratias [16]). Small columns of 3x3x7 mm 3 were cut from this with their long axis parallel to [0/0,0/0,0/2]. Deformation under compression along this axis was performed at 750 °C in an INSTRON 1122 machine in air at a deformation velocity of 0.05 mm/min. A second sample was placed on the lower piston of the machine in order to serve as a reference. Because of a reduced length it was not deformed but went through the same temperature program as the deformation sample. In the following this sample is referred to as the heat-treated sample. After a deformation of 25% the load was released and the samples were quenched in water. Specimens for investigation in the transmission electron microscope (TEM) were prepared from the deformed and the heat-treated samples was well...

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confidence: 63%

“…Yu, Staiger, and Kleman deformed the icosahedral T2 phase of AlLi-Cu by 3% at room temperature and observed dislocations in the TEM [7]. Unfortunately, the authors did not inspect their starting material prior to deformation.…”

Section: Direct Evidence For Plastic Deformation Of Quasicrystals By mentioning

confidence: 89%

Direct evidence for plastic deformation of quasicrystals by means of a dislocation mechanism

et al. 1993

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“…Studies of the defects in QCs have attracted extensive attention because of their importance not only to structural analyses but also to a deep understanding of the mechanical and physical properties of QCs. Dislocations were observed in Al-Mn-Si, Al-Li-Cu and Al-Cu-Fe icosahedral phases by electron microscopy , Chen et al 1987, Devaud-Rzepski et al 1989, Ebalard and Spaepen 1989, Yu et al 1992. In addition, twins (Koskenmaki et al 1986, Dai and Urban 1993, Shield and Kramer 1994, stacking faults (Menon et al 1989, Dai et al 1991, discommensurations (Jiang et al 1991) and domains (Audier et al 1990 have been found experimentally.…”

Section: Dislocations In Qcsmentioning

confidence: 94%

Symmetry groups, physical property tensors, elasticity and dislocations in quasicrystals

2000

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The first quasicrystal (QC) structure was observed in 1984. QCs possess long-range orientational and translational order while lacking the periodicity of crystals. An overview is given on some physical properties of QCs. It begins with group theory and symmetry. Then the thermodynamics of equilibrium properties and physical property tensors are discussed. Finally, the generalized elasticity theory of QCs and the elasticity theory of dislocations in QCs are presented.

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Structural geometry of grain boundaries in icosahedral quasicrystals

Ovid’ko

1994

Z. Physik B - Condensed Matter

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Dislocations observed by transmission electron microscopy in the quasicrystalline phase T2 of Al-Li-Cu after deformation

Cited by 14 publications

References 11 publications

Direct evidence for plastic deformation of quasicrystals by means of a dislocation mechanism

Direct evidence for plastic deformation of quasicrystals by means of a dislocation mechanism

Symmetry groups, physical property tensors, elasticity and dislocations in quasicrystals

Structural geometry of grain boundaries in icosahedral quasicrystals

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