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Zr65Cu17.5Ni10Al7.5 as well as Zr69.5Cu12Ni11Al7.5 belong to the best glass forming alloys known. Glass transition temperatures of melt-spun ribbons are 372 and 360 °C, respectively. TEM and x-ray analysis of samples annealed above the glass transition temperature exhibit the formation of quasicrystalline microstructures with small amounts of crystalline phases. The metastable icosahedral phase is primitive with a quasilattice constant a=0.253 nm; its composition as determined by EDX is close to Zr69.5Cu12Ni11Al7.5. In both glasses, growth of the quasicrystals has been observed to be time-dependent (r∝t1/2), thus indicating a diffusion controlled transformation.

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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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