Accession Number : ADA290817

Title :   Superplastic Ceramics.

Descriptive Note : Final rept. 15 Jun 91-14 Jun 94,

Corporate Author : STANFORD UNIV CA DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Sherby, Oleg D. ; Kim, Woo-Jin

PDF Url : ADA290817

Report Date : 01 SEP 1994

Pagination or Media Count : 10

Abstract : Superplasticity is a newly observed phenomenon in ceramics, with the first publication appearing in 1986. The current program has centered on an experimental study of superplasticity in polycrystalline iron carbide. This material has been made superplastic by utilization of two processing methods: powder processing and ingot-processing. In both cases the end microstructure is a continuous phase of ultra-fine grained iron carbide. The ultra-fine grained powder processed material was successfully gas-pressure blow-formed into a spherical shaped object, and its deformation followed the predicted behavior of a high strain-rate sensitive material that is controlled by grain-boundary sliding. Thermo-mechanical processing routes were developed to refine the coarse as-cast ingot microstructure. Structural refinement is a result of creation of strain-free regions by carbon dissolution from high strain energy subgrain boundaries and slip bands. It is proposed that thermomechanical processing of ingot-cast eutectic-composition oxide ceramics to achieve a superplastic structure is feasible. (jg)

Descriptors :   *CERAMIC MATERIALS, *SUPERPLASTICITY, THERMOMECHANICS, METHODOLOGY, MICROSTRUCTURE, STRUCTURAL PROPERTIES, POWDERS, PROCESSING, COMPOSITE MATERIALS, DEFORMATION, CARBIDES, CARBON, SENSITIVITY, STRAIN RATE, IRON, OXIDES, REFINING, SLIDING, GRAIN BOUNDARIES, FINE GRAINED MATERIALS, POLYCRYSTALLINE, ULTRAFINES.

Subject Categories : Ceramics, Refractories and Glass
      Inorganic Chemistry
      Physical Chemistry
      Plastics

Distribution Statement : APPROVED FOR PUBLIC RELEASE