The Sixth Japan-France Materials Science Seminar
JFMSS-6
Microstructural Design for Improved Mechanical Behaviour of Advanced Materials

J. Phys. IV France 10 (2000) Pr6-79-Pr6-84
DOI: 10.1051/jp4:2000614

An experimental and theoretical study of bonding mechanisms in ternary γ-TiAl + X (X = Cr, Mn, Nb) alloys

M. Jaouen¹, T. Sikora^{1, 2}, G. Hug² and M.G. Walls<sup>3

1</sup>  Laboratoire de Métallurgie Physique, Université de Poitiers, UMR 6630 du CNRS, UFR Sciences SP2MI, boulevard Pierre et Marie Curie, Téléport 2, BP. 30179, 86962 Futuroscope Chasseneuil cedex, France
²  Laboratoire d'Études des Microstructures, UMR 104 du CNRS, ONERA, BP. 72, 92322 Châtillon cedex, France
³  Centre d'Études de Chimie Métallurgique, UPR 2801 du CNRS, 15 rue Georges Urbain, 94407 Vitry-sur-Seine cedex, France

Abstract
The local atomic order and the electronic structure of γ-(Ti₄₆Al₅₄)₉₇X₃ (X = Cr, Mn, Nb) alloys have been investigated by Electron Energy Loss (EELS) and X-ray absorption (XAS) spectroscopies. The substitution sites of solute atoms have been determined experimentally by Atom Location by CHanneling Enhanced MIcroanalysis (ALCHEMI), Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES) in the framework of a multiple scattering (MS) formalism. Furthermore, EXAFS provides a way to probe the local relaxation around the atom of interest. A strong elastic relaxation is found to occur around Mn solute atoms, while Nb solute atoms generate almost no elastic strain. From a calculation in the band structure (BS) formalism, the influence of the ternary solute atom on charge density distribution has been studied and has shown that the addition elements mainly improve the intensity of the d-d bonds within the (001) planes. All these results are consistent with the previously observed mechanical properties and dislocation microstructures.

© EDP Sciences 2000