Les intermétalliques : des superalliages aux quasicristaux
J. Phys. IV France 06 (1996) C2-59-C2-64
Obtention de la phase orthorhombique dans l'alliage Ti52Al30Nb18S. Lokmane1 and M. Guymont1, 2
1 Centre d'Etude de Chimie Métallurgique, CNRS, 15 rue Georges Urbain, 94407 Vitry-sur-Seine cedex, France
2 Laboratoire de Métallurgie Structurale, Université de Paris XI, Bât. 413, 91405 Orsay cedex, France
Several phases may appear in the ternary Ti-Al-Nb, among others : cubic ß, hexagonal α, and (recently identified) orthorhombic O. The special composition Ti52Al30Nb18 has lead to one-phased orthorhombic through adequate thermal treatment. The results of observations using X -ray diffraction, transmission and scanning electron microscopy, are shown. The untreated samples are mainly B2 ; the samples annealed at 1100°C or 900°C, and subsequently quenched, are many-phased α2+O+possibly B2 ; the long annealed (340 h ; 900°C) samples are completely orthorhombic. This final state O seems to be reached, both through a massive transformation B2→O and an ordering α2→O.
© EDP Sciences 1996