MICROSTRUCTURE OF A GAMMA ALPHA-2 BETA TI-AL ALLOY CONTAINING IRON AND VANADIUM

Ordered beta-phase (B2 CsCl structure) has been identified in a Ti-45. 5 at.% Al-1.6 at.% Fe-1.1 at.% V-0.7 at.% B alloy being developed for high temperature applications. Selected area electron diffraction has been used to identify the orientation relationships and interface plan es of the beta-phase with the bulk gamma-TiAl and alpha2-Ti3Al phases. Energy dispersive X-ray spectroscopy indicates that the beta-phase ha s approximately the same Ti/Al ratio as the alpha2-Ti3Al phase, and is stabilized within the microstructure by Fe and V. Channeling enhanced microanalysis studies (ALCHEMI) show that the Fe and V both occupy th e same sublattice as the Al atoms in the cubic beta-phase structure, a nd that Fe occupies the Al sites in the gamma-phase. Fe and V are conc entrated in the beta-phase, which effectively getters these dopants fr om the gamma and alpha2 phases. Titanium ferride precipitates, probabl y FeTi, have been observed within the beta-phase.