Toughening behavior in ceramics associated with the transformation of tetragonal ZrO/sub 2/

Journal Article · Wed Oct 01 00:00:00 EDT 1986 · Acta Metall.; (United States)

DOI:https://doi.org/10.1016/0001-6160(86)90246-4· OSTI ID:7202637

Becher, P F

The contribution of the stress-induced phase transformation ZrO/sub 2/ to the fracture toughness of ceramics is described in terms of the zone size, the critical transformation stress and the influence of these parameters on the tetragonal to monoclinic transformation. For example in partially stabilized zirconia (PSZ), the ..delta..K/sub lC//sup T/ is shown to depend upon the martensite start (M/sub s/) temperature, which can be altered by the solute content and the particle or precipitate size. This behavior is consistent with the thermodynamics of the transformation. Experimental data correspond to the behavior predicted for various systems toughened by the addition of tetragonal ZrO/sub 2/ (e.g. PSZ and Al/sub 2/O/sub 3/-Z/sub 4/O/sub 2/(Y/sub 2/O/sub 3/). The stress required to transform the ZrO/sub 2/ is also modified by residual stresses due to the mismatch in matrix and particle (esp. thermal expansion) properties in the composite systems. The total residual stress acting on a particle is the sum of the particle's internal stress and the stress field of neighboring particles, and as a result, the total residual stress increases with volume fraction of ZrO/sub 2/ (V/sub f/). In the case of the Al/sub 2/O/sub 3/-ZrO/sub 2/ composites the pertinent stresses are tensile in character and thus promote the ZrO/sub 2/ transformation as V/sub f/ increases) For each level of Y/sub 2/O/sub 3/ in the ZrO/sub 2/, ..delta..K/sub lc//sup T/ then goes through a maximum with increase in V/sub f/ at a value of V/sub f/ where sigma/sub R//sup T/ - sigma/sub C//sup T/. The critical transformation stress is thus described for different levels of solute (e.g. Y/sub 2/O/sub 3/) in the ZrO/sub 2/. The dependence of ..delta..K/sub lc//sup T/ upon (sigma/sub C//sup T/ - sigma/sub R//sup T/) obtained is found to agree with the predicted behavior.

• Research Organization: Metals and Ceramics Div., Oak Ridge National Lab., Oak Ridge, TN (US)
• OSTI ID: 7202637
• Journal Information: Acta Metall.; (United States), Vol. 34:10
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
YTTRIUM OXIDES
DISSOLUTION
ZIRCONIUM OXIDES
CRYSTAL-PHASE TRANSFORMATIONS
FRACTURE PROPERTIES
CERAMICS
COMPOSITE MATERIALS
COMPRESSION
DOPED MATERIALS
PRECIPITATION
STRESSES
CHALCOGENIDES
MATERIALS
MECHANICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SEPARATION PROCESSES
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
ZIRCONIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
360202 - Ceramics
Cermets
& Refractories- Structure & Phase Studies