Abstract
The technique of acoustic emission has been shown to be suitable for the monitoring of fracture-toughness tests over a range of temperatures. Commercial polycrystalline alumina has been tested at temperatures up to 1000° C to determine the effect of microstructure and impurity content on fracture toughness and acoustic emission. For a given alumina there was no significant variation in acoustic response or fracture toughness up to 650° C. The emissions observed prior to fracture in this temperature range were attributed to subcritical crack growth. The number of emissions depended on the amount of subcritical crack growth, the grain size, and the presence and amount of porosity. Above 650° C the fracture behaviour changed due to the flow of a grain-boundary glassy phase. This was associated with a peak in the temperature dependence of the apparentK IC and was accompanied by a large number of acoustic events of low amplitude and low pulse width. At these elevated temperatures the extent of grain-boundary glassy flow, and hence the acoustic response, increased with decreasing grain size and increasing impurity content.
Similar content being viewed by others
References
H. Meredith, C. W. A. Newey andP. L. Pratt,Proc. Brit. Ceram. Soc. 20 (1972) 299.
J. Lankford,J. Mater. Sci. 13 (1978) 351.
K. Ryshkewitch,Ber. Dt. Keram. Ges. 22 (1941) 54.
J. Lankford,J. Mater. Sci. 12 (1977) 791.
B. J. Dalgleish, A. Fakhr, P. L. Pratt andR. D. Rawlings,Ber. Dt. Keram. Ges. 55 (1978) 511.
N. Claussen, R. Pabst andC. P. Lahmann,Proc. Brit. Ceram. Soc. 25 (1975) 139.
B. J. Dalgleish, A. Fakhr, P. L. Pratt andR. D. Rawlings, “Physical and Metallurgical Aspects of Acoustic Emission”, (Institute of Acoustics, London, 1977).
Idem, Mater. Sci. Eng. (submitted).
A. A. Pollock,Acoustic Emission 2, Non-Destructive Testing 6 (5) (1973) 223.
A. Fakhr, J. E. Freyre andR. D. Rawlings,Proc. Inst. Acoustics 4 (1976) 1.
R. W. Rice andS. W. Freiman, Presented at the “Sixth International Materials Symposium: Ceramic Microstructures” (Wiley, New York, 1976).
R. W. Rice, “Treatise on Materials Science and Technology”, Vol. II, “Properties and Microstructure” (Academic Press, New York, 1977).
A. G. Evans andG. Tappin,Proc. Brit. Ceram. Soc. 20 (1972) 275.
B. J. Dalgleish, P. L. Pratt andJ. Sandford,Sci. Ceramics 8 (1976) 225.
P. L. Pratt, “Fracture”, Vol. 3 (University of Waterloo Press, Waterloo, 1977) p. 909.
L. A. Simpson andG. J. Merrett,J. Mater. Sci. 9 (1974) 685.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Dalgleish, B.J., Fakhr, A., Pratt, P.L. et al. The temperature dependence of the fracture toughness and acoustic emission of polycrystalline alumina. J Mater Sci 14, 2605–2615 (1979). https://doi.org/10.1007/BF00610629
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00610629