Bulk and defect properties of ordered intermetallics: A first-principles total-energy investigation
First-principles quantum mechanical calculations based on local-density-functional theory have been used to investigate the fundamental factors that govern the deformation and fracture behavior of ordered intermetallic alloys. Unlike in Ni{sub 3}Al, the calculated elastic constants and shear fault energies indicate that anomalous yield strength behavior is not likely to occur in Ni{sub 3}Si. From the calculated Griffith strength and a phenomenological theory relating fracture toughness to ideal cleavage strength, Ni{sub 3}Si is predicted to be ductile with respect to cleavage fracture. For TiAl, we find the absence of structural vacancies due to the strong Ti-Al bonding and similar atomic radii for Ti and Al. For NiAl, the defect structure is found to be dominated by two types of defects - monovacancies on the Ni sites and substitutional antisite defects on the Al sites. For FeAl, on the other hand, we find a more complex defect structure, which is closely related to the importance of electronic structure effect in FeAl. More importantly, we predict the strong tendency for vacancy clustering in FeAl due to the large binding energy found for divacancies. Effects of thermomechanical history on microhardness are discussed in terms of the calculated results.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 10163121
- Report Number(s):
- CONF-921101--124; ON: DE93015492
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360103
665000
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM ALLOYS
BINDING ENERGY
ELECTRONIC STRUCTURE
INTERMETALLIC COMPOUNDS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
NICKEL BASE ALLOYS
PHYSICS OF CONDENSED MATTER
POINT DEFECTS
QUANTUM MECHANICS
VACANCIES