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Journal of Materials Science

, Volume 15, Issue 1, pp 96–102 | Cite as

Observations on the effect of calcium segregation on the fracture behaviour of polycrystalline alumina

  • R. S. Jupp
  • D. F. Stein
  • D. W. Smith
Papers

Abstract

The influence of calcium segregation to the grain boundaries of polycrystalline alumina on room temperature fracture behaviour has been investigated. In a commercial high-density single-phase alumina containing less than 5 ppm calcium by weight, thermal treatments were employed to achieve equilibrium segregation from 0.6 to 1.6 at % calcium without detectable changes in grain size (18μm) or porosity distribution. Room temperature SENB test results revealed an inverse dependence of KIC on calcium segregation levels in the range examined. Fractures were primarily intergranular in all specimens. Qualitatively, the relationship between KIC and calcium segregation would be predicted from a consideration of the effect of such an ion on the interatomic spacing at the boundary. However, quantitative agreement with the model is poor, the measured effect being much greater than predicted. A relatively high KIC value was achieved in a fine grained (2μm) hot-pressed alumina containing very low levels of segregated impurities. This material exhibited substantial amounts of cleavage fracture. The higher fracture toughness of this alumina is discussed in terms of both increased intergranular and transgranular fracture stresses promoted by the relatively clean grain boundaries and small grain size, respectively.

Keywords

Fracture Toughness Fracture Behaviour Cleavage Fracture Fine Grained High Fracture Toughness 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Chapman and Hall Ltd. 1980

Authors and Affiliations

  • R. S. Jupp
    • 1
  • D. F. Stein
    • 1
  • D. W. Smith
    • 1
  1. 1.Department of Metallurgical EngineeringMichigan Technological UniversityHoughtonUSA

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