1ST-PRINCIPLES STUDY OF PHASE-STABILITY OF TI-AL INTERMETALLIC COMPOUNDS

Thermodynamic and structural properties of fcc- and hcp-based Ti-Al al loys are calculated from first-principles and are used to perform an a b initio study of phase stability for the intermetallic compounds in t his system. The full potential linear muffin tin orbital method is use d to determine heats of formation and other zero-temperature propertie s of 9 fcc- and 7 hcp-based intermetallic compounds, as well as of ele mental fcc and hcp Ti and Al. From the results of these calculations, sets of effective cluster interactions are derived and are used in a c luster variation method calculation of the solid-state portion of the composition-temperature phase diagram for fcc- and hcp-based alloy pha ses. The results of our calculations are compared with those of experi mental studies of stable and metastable phases in the Ti-Al system.