Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/41630

Title

Acoustic emission studies of alumina-13% titania free-standing forms during four-point bend tests

Author(s)

Lin, Chung Kwei;  Berndt, Christopher C.;  Leigh, Sang Ha;  Murakami, Kenji

Abstract

Free-standing alumina-13% titania samples were manufactured with a water-stabilized plasma spray gun to a thickness of ∼5 mm. A thin layer of aluminum was arc sprayed prior to depositing the thick coating and etched away using hydrochloric acid. The so-obtained free-standing plate was cut into four-point-bend-test specimens with dimensions of ∼5 mm × 5 mm × 50 mm. The assprayed material consisted of a supersaturated solid solution, where titania was frozen inside the alumina matrix. Heat treatment was performed at 1450°C for 24 h and then at 1100°C for another 24 h. After heat treatment, titania precipitates were observed. The major phases of the assprayed and heat-treated samples were γ- and α-alumina, respectively. The porosity was ∼10% for as-sprayed samples; this value was reduced to ∼3% after heat treatment. Four-point bend tests were performed on the assprayed and heat-treated specimens in cross-section and in-plane directions. An acoustic emission technique was used to examine the cracking during the tests in situ. Microcracking prior to failure was observed for as-sprayed samples that were tested in the cross-section direction. However, when tested in the in-plane direction, catastrophic failure with less evidence of microcracking occurred. For heat-treated specimens, microcracks were usually observed when tests were performed in either of the orientations. Energy and amplitude distributions for each testing condition were examined. These distributions changed after heat treatment; however, no significant differences were distinguished when tests were performed in the cross-section or in-plane directions.

Publication type

Journal article

Source

Journal of the American Ceramic Society, Vol. 80, no. 9 (Sep 1997), pp. 2382-2394

Publication year

1997

Keyword(s)

Acoustic emissions;  Alumina;  Crack initiation;  Crack propagation;  Failure (mechanical);  Four point bend testing;  Free standing form;  Heat treatment;  Mechanical testing;  Microcracks;  Microstructure;  Plasma spraying;  Porosity;  Titania

Publisher

American Ceramic Society

ISSN

0002-7820

Publisher URL

http://dx.doi.org/10.1111/j.1151-2916.1997.tb03130.x

Copyright

Copyright © 2008 American Ceramic Society.

Additional information

This research program is supported by the National Science Foundation under the STRATMAN Program, No. DDM 9215846. The authors also acknowledge the support of NSF-MRSEC-DMR 9632570. This work also is part of a fundamental study on 'cracking mechanisms', which is partially supported by the Alcoa Foundation.

Peer reviewed