Transformation toughening of ceramics. Final report, 15 Jan 89-14 Jan 92

Technical Report · Sun Mar 01 04:00:00 EST 1992

OSTI ID:5165134

Marshall, D B

The results of a three-year study, aimed at developing a fundamental understanding of transformation toughening in ceramics and using that understanding to design and fabricate new microstructures with improved properties, are described. A new class of materials with dual scale (laminar) microstructures and greatly enhanced fracture toughness have been developed and tested; Increases In fracture toughness from 5 to 18 MPAm(to the l/2 power) were measured. These new microstructures were designed by combining micromechanics modeling of the effects of zone shape on toughness with direct measurements of transformation zone characteristics (which provided critical testing of the theoretical modeling) and measurements of transformation thermodynamics. To fabricate these microstructures a now colloidal processing method, which allowed construction of multilayered structures with layer thicknesses as small as 10 microns Lm, was developed. The direct transformation zone measurements included Raman microprobe spectroscopy to measure the distribution of transformed phases within the zones, and moire interferometry and high resolution strain mapping (by digital image correlation) to measure directly the transformation strains that are responsible for toughening. Calculations of crack tip shielding indicated modifications to transformation zone shapes that would increase the toughening.

• Research Organization: Rockwell International Corp., Thousand Oaks, CA (United States). Science Center
• OSTI ID: 5165134
• Report Number(s): AD-A-248903/7/XAB; SC--71002.FR; CNN: F49620-89-C-0031
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360203 -- Ceramics
Cermets
& Refractories-- Mechanical Properties
CERAMICS
COMPOSITE MATERIALS
CRACKS
CRYSTAL STRUCTURE
DISTRIBUTION
ELEMENTS
FABRICATION
FRACTURE PROPERTIES
IMAGES
INTERFEROMETRY
MATERIALS
MECHANICAL PROPERTIES
MECHANICS
METALS
MICROSTRUCTURE
PROCESSING
RESOLUTION
SHAPE
SHIELDING
SPECTROSCOPY
THERMODYNAMICS
TRANSITION ELEMENTS
ZIRCONIUM