Accession Number : ADA299692

Title :   Transformation Toughening of Ceramics.

Descriptive Note : Final rept. 1 Apr 92-30 Apr 95,

Corporate Author : ROCKWELL INTERNATIONAL THOUSAND OAKS CA SCIENCE CENTER

Personal Author(s) : Marshall, D. B.

PDF Url : ADA299692

Report Date : SEP 1995

Pagination or Media Count : 19

Abstract : This report summarizes the results from a 3-year research program aimed at developing a basic understanding of the microstructural design, fabrication, and properties of multilayered zirconia-based composites with high toughness and oxidation resistance. Most of the effort focused on multilayered composites of Ce-ZrO2 and Al2O3 which have strongly bonded interfaces. The design of the layered composite microstructure was based on micromechanics analysis: the layers modify the shape and extent of a crack tip transformation zone, leading to toughnesses over 20 MPa.m1/2. Optimum layer thicknesses were determined and related to effects of autocatalytic transformation and crack tip advance mechanisms. Crack resistance curves were measured at various temperatures: the very high toughnesses (> 10 MPa.m1/2) were limited to temperature range of approx. 100 deg C above the Ms temperature for the martensitic transformation. A preliminary study of multilayered composites containing weakly bonded layers (which achieve toughening by debonding) indicated that rare earth phosphates (LaPO4 and CePO4) are potentially suitable layers for Y- and Ce-stabilized zirconia composites. jg

Descriptors :   *TOUGHNESS, *CERAMIC MATERIALS, *ALUMINUM OXIDES, *CERIUM, *ZIRCONIUM, *TRANSFORMATIONS, TEMPERATURE, THICKNESS, MICROSTRUCTURE, OPTIMIZATION, INTERFACES, LAYERS, COMPOSITE MATERIALS, CRACKS, BONDED JOINTS, OXIDATION RESISTANCE, RANGE(EXTREMES), MICROMECHANICS, RARE EARTH ELEMENTS, PHOSPHATES, MARTENSITE.

Subject Categories : Inorganic Chemistry
      Ceramics, Refractories and Glass
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE