Processing of novel nanoparticle dispersion strengthened ceramics for improved mechanical performance. Annual report No. 2, 15 December 1992-14 December 1993
Results from a previous study carried out by the Lehigh group demonstrated Al2O3:SiC nanocomposites exhibited superior mechanical behavior relative to single phase alumina only when the samples had been annealed (2 h at 1300 deg C in argon) subsequent to industrial machining. These results were rationalized by postulating that on annealing of the machined specimens: (a) The extent of healing of grinding induced flaws is more significant in the nanocomposite than in alumina. (b) The machining induced residual stresses are relaxed to a lesser degree in the nanocomposite than in alumina. Further model studies have now been carried out which provide definitive evidence that both of the above assumptions are correct. Observation of indentation induced cracks both prior to, and after annealing, revealed that in the nanocomposite cracking is predominantly transgranular, and crack healing takes place on annealing. For the case of single phase alumina, however, the crack morphology is predominantly intergranular, and annealing causes crack growth.
- Research Organization:
- Lehigh Univ., Bethlehem, PA (United States). Materials Research Center
- OSTI ID:
- 7072502
- Report Number(s):
- AD-A-275965/2/XAB; CNN: N00014-92-J-1635
- Country of Publication:
- United States
- Language:
- English
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360201 -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360203 -- Ceramics
Cermets
& Refractories-- Mechanical Properties
360601* -- Other Materials-- Preparation & Manufacture
360603 -- Materials-- Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBIDES
CARBON COMPOUNDS
CERAMICS
CHALCOGENIDES
COMPOSITE MATERIALS
CRACK PROPAGATION
DOCUMENT TYPES
MATERIALS
MECHANICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PROGRESS REPORT
RESIDUAL STRESSES
SILICON CARBIDES
SILICON COMPOUNDS
STRESSES
SYNTHESIS