Strengthening of Oxide Ceramics by Transformation‐Induced Stress

ANIL V. VIRKAR, JOW LAY HUANG, RAYMOND A. CUTLER

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Abstract

Alumina‐zirconia composites were fabricated by isostatic pressing and sintering of powder mixtures in such a way that bar‐shaped specimens consisted of three layers. The outer layers contained A12O3 and unstabilized ZrO2 while the central layer contained A12O3 and partially stabilized ZrO2 (with 2 mol% Y2O3). When cooled from the sintering temperature, some of the zirconia in the outer layers transformed to the monoclinic form while zirconia in the central layer was retained in the tetragonal form. The transformation of zirconia in the outer layers led to the establishment of surface compressive stresses and balancing tensile stresses in the bulk. The existence of surface compressive stresses was verified by a strain gauge technique and bending strength measurements on samples with varying thickness of the outer layers. The layered composites exhibited greater strength in comparison with monolithic Al2O3‐ZrO2 specimens. Further, variation of strength in bending with outer layer thickness (for a fixed total thickness) indicated that failure occurred from internal flaws. Scanning electron microscopy of fracture surfaces revealed that strength‐limiting flaws were voids located in the central layer near the interface separating the central and the outer layers.

Original languageEnglish
Pages (from-to)164-170
Number of pages7
JournalJournal of the American Ceramic Society
Volume70
Issue number3
DOIs
Publication statusPublished - 1987 Mar

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

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