Mechanics and structure of dislocations induced by thermal mismatch in composite materials

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5470006

Dunand, D C

Cast silver chloride containing alumina or glass spheres, particles, or fibers is used as a model material for metal-matrix composites to study thermally induced plasticity around large inclusions. Matrix dislocations, resulting from the thermal mismatch between reinforcement and matrix upon quenching of the composite, are decorated at room temperature in the bulk through photodissociation of the matrix and observed by optical microscopy. The plastic zone is found to take the form of (1) a deformed region surrounding the inclusion and containing a high density of dislocation tangles, (2) rows of prismatic, interstitial dislocation loops punched into the matrix and extending at a large distance from the interface. From the number of loops punched by spheres and that punched radially by fibers, the highest temperature at which slip is operative is found to be 400 {plus minus} 30 K. The residual elastic stress in the plastic zone around fibers is determined from the radius of curvature of pinned dislocation, leading to the conclusion that the matrix is strain-hardened. Another model predicting the number of loops punched at fiber ends is developed.

• Research Organization: Massachusetts Inst. of Tech., Cambridge, MA (United States)
• OSTI ID: 5470006
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602 -- Other Materials-- Structure & Phase Studies
360603* -- Materials-- Properties
COMPOSITE MATERIALS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DISLOCATIONS
ELEMENTS
HARDENING
LINE DEFECTS
MATERIALS
MATRIX MATERIALS
MECHANICAL PROPERTIES
METALS
PLASTICITY
RESIDUAL STRESSES
STRAIN HARDENING
STRESSES
STRUCTURAL MODELS