Slip, twinning, and fracture at a grain boundary in the L1/sub 2/ ordered structure: A. sigma. = 9 tilt boundary

Journal Article · Thu Sep 01 04:00:00 EDT 1988 · J. Mat. Res.; (United States)

OSTI ID:6911113

Yoo, M H; King, A H

The role of interaction between slip dislocations and a ..sigma.. = 9 tilt boundary in localized microplastic deformation, cleavage, or intergranular fracture in the L1/sub 2/ ordered structure has been analyzed by using the anisotropic elasticity theory of dislocations and fracture. Screw superpartials cross slip easily at the boundary onto the (11-bar1) and the (001) planes at low and high temperatures, respectively. Transmission of primary slip dislocations onto the conjugate slip system occurs with a certain degree of difficulty, which is eased by localized disordering. When the transmission is impeded, cleavage fracture on the (1-bar11) plane is predicted to occur, not intergranular fracture, unless a symmetric double pileup occurs simultaneously. Absorption (or emission) of superpartials occurs only when the boundary region is disordered. Slip initiation from pre-existing sources near the boundary can occur under the local stress concentration. Implications of the present result on the inherent brittleness of grain boundaries in Ni/sub 3/ Al and its improvement by boron segregation are discussed.

• Research Organization: Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
• OSTI ID: 6911113
• Journal Information: J. Mat. Res.; (United States), Journal Name: J. Mat. Res.; (United States) Vol. 3:5; ISSN JMREE
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
656002 -- Condensed Matter Physics-- General Techniques in Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
ALUMINIUM ALLOYS
BRITTLENESS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DISLOCATIONS
FRACTURE MECHANICS
GRAIN BOUNDARIES
INTERMETALLIC COMPOUNDS
LINE DEFECTS
MECHANICAL PROPERTIES
MECHANICS
MICROSTRUCTURE
NICKEL ALLOYS
SLIP
STRESSES
TWINNING