Microstructural evolution and micromechanical modeling of the mechanical behavior of a ceramic particle-reinforced metal-matrix composite

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:6905579

Christman, T A

The objective was to develop a thorough understanding of the precipitation characteristics and mechanical behavior of a 2124 Al-SiC Aluminum alloy reinforced with 13.2 volume% SiC whiskers. Microstructural development of the 2124 Al-SiC composite subject to controlled and systematic aging treatments was investigated. The results indicate that the matrix of the composite material has a much greater dislocation density than the control alloy. The increased dislocation density facilitates the nucleation of the strengthening precipitates whereby the incubation time for precipitate nucleation and the time to reach peak hardness in the matrix of the composite are significantly reduced. Theoretical analysis of dislocation generation due to thermal contraction mismatch and of the punching of dislocations at whisker ends are examined in the context of microstructural development. An experimental and theoretical investigation into the uniaxial: stress-strain response of the 2124 Al-SiC whisker composite system was undertaken where the effects of accelerated aging of the matrix of the composite were incorporated into the modeling of deformation behavior. The 0.2% offset yield strength was found to be independent of aging state, whereas the strain to failure was found to decrease monotonically with an increase in aging time for the composite. A self consistent approximation was formulated and was found to provide the most accurate predictions for the elastic response of the composite. A finite-element unit-cell model was used to predict the plastic response of the composite material. The effects of SiC reinforcement and matrix aging treatment on crack growth under quasi-static and fatigue loading were also investigated. The composite exhibits a fatigue threshold value which is about twice that of the control alloy.

• Research Organization: Brown Univ., Providence, RI (USA)
• OSTI ID: 6905579
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
AGING
ALLOYS
ALUMINIUM ALLOYS
BENCH-SCALE EXPERIMENTS
CARBIDES
CARBON COMPOUNDS
COMPOSITE MATERIALS
CRACK PROPAGATION
CRYSTAL STRUCTURE
CRYSTALS
DATA
INFORMATION
MATERIALS
MATRIX MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
MONOCRYSTALS
NUMERICAL DATA
SILICON CARBIDES
SILICON COMPOUNDS
STRAIN AGING
STRESS ANALYSIS
THEORETICAL DATA
WHISKERS