Characterization and defect analysis of high temperature aluminum-based metal matrix composites
There is a need for an aluminum-based material to replace titanium in high temperature aerospace applications. Two powder metallurgy (P/M) matrices, RSP Al-8Fe-4Ce and MA Al-9Ti reinforced with 20 volume percent Al2O3 fibers or SiC whiskers or particles were developed for this purpose. Microstructural and mechanical property evaluations of these systems were performed to determine high temperature viability. Elevated temperature tensile tests demonstrated strengths of 14 ksi (98 MPa) at 450 C in the RSP matrix composites reinforced with SiC whiskers; the MA Al-9Ti materials produced tensile strengths of better than 17 ksi (120 MPa) at 500 C. Processing defects contribute significantly to tensile failure at low temperature; Co/SiC defects that result from a sol gel processing step coarsen with exposure to elevated temperature. At elevated temperatures, the failure of all composites was matrix controlled, although some particulate strengthening is evident. A fracture mechanics approach was utilized to determine the plane strain fracture toughness of Al-9Ti/Co/SiC particle reinforced composites; K(sub IC) at room temperature in the as received condition is 4.7 MPa-m(exp 1/2). Fracture toughness increased with annealing at 500 C for 120 and 400 hours. The growth of the intermetallic reaction zone in the Co/SiC particle reinforced materials was found to be parabolic; the rate constants were determined as a function of temperature. Moving boundary theory was applied to determine the interdiffusion coefficient in the intermetallic region as a function of temperature; diffusion is enhanced by a subgrain structure in the reaction zone although a determination of the pre-exponential factor and activation energy for interdiffusion does not show this effect. The pre-exponential interdiffusion coefficient, D(sub 0) is equal to 7.0 x 10(exp 11) sq m/sec and the activation energy for interdiffusion is Q = 99.9 kcal.
- Research Organization:
- Virginia Univ., Charlottesville, VA (United States)
- OSTI ID:
- 6631154
- Resource Relation:
- Other Information: Ph.D. Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM BASE ALLOYS
MECHANICAL PROPERTIES
POWDER METALLURGY
TENSILE PROPERTIES
REINFORCED MATERIALS
MICROSTRUCTURE
THERMODYNAMIC PROPERTIES
ALUMINIUM ALLOYS
ALUMINIUM OXIDES
ANNEALING
CERIUM ALLOYS
COMPOSITE MATERIALS
DEFECTS
DIFFUSION
FIBERS
FRACTURE MECHANICS
FRACTURE PROPERTIES
IRON ALLOYS
MATRICES
MATRIX MATERIALS
PARTICLES
PROCESSING
SILICON CARBIDES
SOL-GEL PROCESS
TITANIUM ALLOYS
WHISKERS
ALLOYS
ALUMINIUM COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
CRYSTAL STRUCTURE
CRYSTALS
HEAT TREATMENTS
MATERIALS
MECHANICS
METALLURGY
MONOCRYSTALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH ALLOYS
SILICON COMPOUNDS
360603* - Materials- Properties
360606 - Other Materials- Physical Properties- (1992-)
360601 - Other Materials- Preparation & Manufacture