Bulk and defect properties of ordered intermetallics

Conference · Fri Dec 31 04:00:00 EST 1993

OSTI ID:10177773

Fu, C L; Yoo, M H

First-principles calculations based on the local-density-functional theory have been used to investigate the factors governing strength of ordered intermetallic alloys. Unlike Ni{sub 3}Al, calculated elastic constants and shear fault energies indicate 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 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, absence of structural vacancies and deviations from stoichiometry are accommodated by substitutional antisite defects on both sublattices. Intrinsic strengthening mechanisms in TiAl are discussed in terms of calculated elastic constants and shear fault energies. Because of reduced fault energies at the {gamma}/{alpha}{sub 2} interface, slip and twinning contribute significantly to high shear deformation of the lamellar structure.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 10177773
• Report Number(s): CONF-931009--29; ON: DE94017706
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103
ALUMINIUM ALLOYS
INTERMETALLIC COMPOUNDS
MECHANICAL PROPERTIES
NICKEL BASE ALLOYS
NICKEL SILICIDES
POINT DEFECTS
TITANIUM ALLOYS