Numéro
J. Phys. IV France
Volume 04, Numéro C3, Février 1994
36ème Colloque de Métallurgie de l'INSTN
CHANGEMENTS DE PHASES ET MICROSTRUCTURES
Page(s) C3-169 - C3-174
DOI http://dx.doi.org/10.1051/jp4:1994324
36ème Colloque de Métallurgie de l'INSTN
CHANGEMENTS DE PHASES ET MICROSTRUCTURES

J. Phys. IV France 04 (1994) C3-169-C3-174

DOI: 10.1051/jp4:1994324

Transition de phases réversible icosaédrique - rhomboédrique de l'alliage Al63,5Fe12,5Cu24

N. MENGUY, M. AUDIER, P. GUYOT and M. DE BOISSIEU

Laboratoire de Thermodynamique et Physico-Chimie Metallurgiques, UA 29 du CNRS, ENSEEG, BP. 75, 38402 Saint Martin d'Hères, France


Abstract
A reversible phase transformation between icosahedral and rhombohedral structures has been studied by transmission electron microscopy. Some transient states have been characterised by x-ray diffraction using a 4 circles goniometer on a synchrotron beam line. The microcrystalline rhombohedral phase is stable at low temperature ; above 675°C it transforms into an icosahedral phase via an intermediate pentagonal structure. The icosahedral phase, metastable at low temperature, transforms between 500 and 675°C into the rhombohedral phase via different transient states : modulated icosahedral phases and pentagonal approximants. These intermediate states have been interpreted as resulting of shear waves of phason type, propagating along the basis vectors of a 6-D hyper cubic lattice and polarized along the perpendicular space. The chemical composition variations associated to these shear waves and predicted by the theory have been experimentally observed.



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