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

The local atomic order and the electronic structure of gamma-(Ti46Al54)(97) X-3 (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 CHann eling Enhanced Microanalysis (ALCHEMI), Extended X-ray Absorption Fine Stru cture (EXAFS) and X-ray Absorption Near Edge Structure (XANES) in the frame work of a multiple scattering (MS) formalism. Furthermore, EXAFS provides a way to probe the local relaxation around the atom of interest. A strong el astic relaxation is found to occur around Mn solute atoms, while Nb solute atoms generate almost no elastic strain. From a calculation in the band str ucture (BS) formalism, the influence of the ternary solute atom on charge d ensity distribution has been studied and has shown that the addition elemen ts mainly improve the intensity of the d-d bonds within the (001) planes. A ll these results are consistent with the previously observed mechanical pro perties and dislocation microstructures.