Influence of the ZrO[sub 2] grain size and content on the transformation response in the Al[sub 2]O[sub 3]-ZrO[sub 2] (12 mol% CeO[sub 2]) system

Journal Article · Mon Mar 01 04:00:00 EST 1993 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1993.tb03656.x· OSTI ID:6050536

Becher, P F; Alexander, K B; Bleier, A; Waters, S B; Warwick, W H ^[1]

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1. Oak Ridge National Lab., TN (United States)

Based on experimental and modeling studies, the rate of increase in the martensite start temperature M[sub s] for the tetragonal-to-monoclinic transformation with increase in zirconia grain size is found to rise with decrease in ZrO[sub 2] content in the zirconia-toughened alumina ZTA system. The observed grain size dependence of M[sub s] can be related to the thermal expansion mismatch tensile (internal) stresses which increase with decrease in zirconia content. The result is that finer zirconia grain sizes are required to retain the tetragonal phase as less zirconia is incorporated into the alumina, in agreement with the experimental observations. At the same time, both the predicted and observed applied stress required to induce the transformation are reduced with increase in the ZrO[sub 2] grain size. In addition, the transformation-toughening contribution at temperature T increases with increase in the M[sub s] grain size, when T>M[sub s]. In alumina containing 20 vol% ZrO[sub 2] (12 mol% CeO[sub 2]), a toughness of [approximately]10 MPa [center dot] [radical]m can be achieved for a ZrO[sub 2] grain size of [approximately]2 [mu]m (M[sub s] [approximately]225K). However, at a grain size of [approximately]2[mu]m, the alumina-40 vol% ZrO[sub 2] (12 mol% CeO[sub 2]) has a toughness of only 8.5 MPa [center dot] [radical]m (M[sub s] [approximately] 150K) but reaches 12.3 MPa [center dot] [radical]m (M[sub s] [approximately] 260K) at a grain size of [approximately]3 [mu]m. These findings show that composition (and matrix properties) play critical roles in determining the ZrO[sub 2] grain size to optimize the transformation toughening in ZrO[sub 2]-toughened ceramics.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6050536
• Journal Information: Journal of the American Ceramic Society; (United States), Journal Name: Journal of the American Ceramic Society; (United States) Vol. 76:3; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CERIUM COMPOUNDS
CERIUM OXIDES
CHALCOGENIDES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
EXPANSION
FRACTURE PROPERTIES
GRAIN SIZE
MECHANICAL PROPERTIES
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHASE TRANSFORMATIONS
RARE EARTH COMPOUNDS
SIZE
STRESSES
TETRAGONAL LATTICES
THERMAL EXPANSION
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES