Numéro |
J. Phys. Colloques
Volume 38, Numéro C7, Décembre 1977
COLLOQUE INTERNATIONAL du C.N.R.S.L'ORDRE ET LE DÉSORDRE DANS LES SOLIDES / ORDER AND DISORDER IN SOLIDS |
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Page(s) | C7-364 - C7-364 | |
DOI | https://doi.org/10.1051/jphyscol:1977771 |
L'ORDRE ET LE DÉSORDRE DANS LES SOLIDES / ORDER AND DISORDER IN SOLIDS
J. Phys. Colloques 38 (1977) C7-364-C7-364
DOI: 10.1051/jphyscol:1977771
THE FORMATION OF VACANCIES IN ORDERED Fe-Al ALLOYS WITH B2 STRUCTURE
D. PARIS and P. LESBATSDépartement de Métallurgie, Ecole des Mines de Saint-Etienne, France
Abstract
The vacancies retained by quenching or at thermal equilibrium were studied experimentally in ordered Fe-Al alloys with B2 structure over a range of compositions from 46 to 51 at % Al. The study, which was initially mainly dilatometric, shows that : - The formation of vacancies is a property of the B2 structure in iron-aluminium. - Quenching is very efficient for retaining vacancies at least up to 1 000°C. - At constant temperatures, the concentration of vacancies increases monotically with the aluminium content and can reach very high values (> 2 %). - At constant aluminium content, the vacancy concentration as a function of temperature exhibits an anomaly characterized by a negative deviation from the classical exponential law. The temperature at which this anomalous behaviour is observed is independent of aluminium content and is equal to 1 000°C. A systematic study of the possible causes allows one to conclude that this anomaly must be related to a decrease in the degree of order. This study was completed by observations using field ion microscopy which shows that : - The vacancy interpretation of the effects previously observed by different methods is correct. - It is possible to evaluate the distribution of vacancies among both sub-lattices, and that the quenched vacancies preferentially occupy iron sites.