Bulk and defect properties of ordered intermetallics

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:72416

Fu, C L; Yoo, M H ^[1]

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1. Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

First-principles calculations based on the local-density-functional theory have been used to investigate the fundamental factors that govern the strength 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. This suggests the inadequacy of cross-slip-pinning model to explain the strength anomaly in the L1{sub 2} structure. For strongly ordered 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. By contrast, for Ni{sub 3}Al, the authors find the absence of structural vacancies and the deviations from stoichiometry are accommodated by substitutional antisite defects on both sublattices. Intrinsic strengthening mechanisms in TiAl are discussed in terms of the calculated elastic constants and shear fault energies. Because of the reduced fault energies at the {gamma}/{alpha}{sub 2} interface, slip and twinning contribute significantly to high shear deformation of the lamellar structure.

• OSTI ID: 72416
• Report Number(s): CONF-9310224--; ISBN 0-87339-249-3
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
ATOMIC MODELS
ELASTICITY
ELECTRONIC STRUCTURE
INTERMETALLIC COMPOUNDS
LATTICE PARAMETERS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
NICKEL ALLOYS
PLATINUM ALLOYS
POINT DEFECTS
POISSON RATIO
POTENTIALS
SCANDIUM ALLOYS
SILICON ALLOYS
TITANIUM ALLOYS
VACANCIES
YIELD STRENGTH