Density of thermal vacancies in {gamma}-Ti-Al-M, M = Si, Cr, Nb, Mo, Ta or W

Journal Article · Tue Oct 26 04:00:00 EDT 1999 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(99)00231-1· OSTI ID:20002022

Woodward, C; Kajihara, S

Modifications to alloy chemistry are often used to tailor the intrinsic flow behavior of structural materials. Models of creep in intermetallic alloys must account for the influence of chemistry on the available intrinsic creep mechanisms. As in simple metals the presence of vacancies strongly influences bulk diffusion processes in these materials. Limiting the density of constitutional and thermal vacancies by alloying may produce materials with enhanced creep properties. The energy of intrinsic and substitutional point defects in L1{sub 0} TiAl is calculated within a first principles, local density functional theory framework. Relaxed structures and energies for vacancies, antisites and solid solutions are calculated using a plane-wave-pseudopotential method. Calculated defect energies are used within a canonical ensemble formalism to estimate the point defect densities as a function of temperature and composition. The density of vacancies is found to be sensitive to the underlying stoichiometry of TiAl. The dependence of the vacancy concentration for solid solutions of Si, Cr, Nb, Mo, Ta and W is also predicted.

• Research Organization: Air Force Research Lab., Wright Patterson AFB, OH (US)
• OSTI ID: 20002022
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 14 Vol. 47; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CHEMICAL COMPOSITION
CHROMIUM ALLOYS
CREEP
INTERMETALLIC COMPOUNDS
MATHEMATICAL MODELS
MOLYBDENUM ALLOYS
NIOBIUM ALLOYS
SILICON ALLOYS
TANTALUM ALLOYS
TEMPERATURE DEPENDENCE
TITANIUM ALLOYS
TUNGSTEN ALLOYS
VACANCIES