Crack‐tip Degradation Processes Observed during in situ Cyclic Fatigue of Partially Stabilized Zirconia

Mark Hoffman, Yiu‐Wing ‐W Mai, Shuichi Wakayama, Masanori Kawahara, Teruo Kishi

Research output: Journal article publicationJournal articleAcademic researchpeer-review

15 Citations (Scopus)

Abstract

It is proposed that reduced transformation zone widths in Mg‐PSZ in cyclically versus critically propagated cracks are due to reductions in the crack‐tip toughness, consistent with an intrinsic cyclic fatigue mechanism. Cyclic fatigue crack growth in Mg‐PSZ was observed in situ in a SEM. Following cyclic fatigue, the samples were critically broken and the fracture surfaces observed. Extensive crack bridging by the precipitate phase was observed near the crack tip, and it is proposed that this crack bridging significantly affects the material's intrinsic toughness. Frictional degradation of the precipitate bridges occurs during cyclic loading and hence reduces the critical crack‐tip stress intensity factor for crack propagation. Reductions in the critical crack‐tip stress intensity factor also lead to reductions in the transformation zone widths during cyclic loading and hence the level of crack‐tip shielding caused by phase transformation. This appears to be the mechanism of cyclic fatigue. A degree of uncracked ligament bridging was also observed and is linked with the frequency of random large precipitates. However, analysis shows that its effect upon crack growth rates under cyclic load is limited.

Original languageEnglish
Pages (from-to)2801-2810
Number of pages10
JournalJournal of the American Ceramic Society
Volume78
Issue number10
DOIs
Publication statusPublished - Oct 1995
Externally publishedYes

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry

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