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Sintering Conditions, Microstructure and Properties of Alumina 10 vol% Zirconia Nanocomposites
F. Kern
Institut für Fertigungstechnologie keramischer Bauteile, Universität Stuttgart, (Institute for Manufacturing Technologies of Ceramic Components and Composites, University of Stuttgart), 70569 Stuttgart, Allmandring 7b, Germany
received September 21, 2011, received in revised form October 5, 2011, accepted October 12, 2011
Vol. 3, No. 1, Pages 1-8 DOI: 10.4416/JCST2011-00036
Abstract
Zirconia-toughened alumina (ZTA) ceramics of various compositions have high relevance in the field of mechanical engineering for cutting tools and wear parts as well as in biomedical applications for hip and knee implants.
In this study a matrix of submicron size α-alumina is reinforced with 10 vol% unstabilized zirconia nanoparticles. The ZTA ceramics were consolidated by means of hot pressing at 1400 – 1550 °C at 60 MPa axial pressure for 1 h in order to test the influence of the sintering conditions on the mechanical properties, microstructure and phase composition. Despite the conventional mixing and milling method used, ZTA nanocomposites of high homogeneity were obtained. Low sintering temperatures result in ultra-fine-grained materials with high hardness. High strength of 900 – 1050 MPa was observed over the whole sintering temperature range, while toughness rises with sintering temperature. A clear correlation between transformability of the tetragonal phase and toughness cannot be identified. Highest strength was found for ZTA with a low initial monoclinic content and high transformability. Increasing sintering temperatures led to only slight microstructural coarsening but to a migration of zirconia particles and rising monoclinic content. Associated with these effects, a gradual shift from transformation toughening to microcrack toughening was observed.
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Keywords
ZTA, nanocomposite, microstructure, phase composition
References
1 Hannink, R., Kelly, P., Muddle, B.: Transformation toughening in zirconia-containing ceramics, J. Am. Ceram. Soc., 83, [3], 461 – 87, (2000).
2 Claussen, N.: Fracture toughness of Al2O3 with an unstabilized ZrO2 dispersed phase, J. Am. Ceram. Soc., 59, [1 – 2], 49 – 51, (1976).
3 Wang, X., Tian, J., Yu, X., Shan, Y, Liu, Z., Yin, Y: Effect of microstructure on the fracture behavior of micro-nano ZTA composite, Mat. Chem. Phys., 112, 213 – 217, (2008).
4 Lange, F.F., Hirlinger, M.: Hindrance of grain growth in Al2O3 by ZrO2 inclusions, J. Am. Ceram. Soc., 67, [3], 164 – 168, (1982).
5 Heuer, A.H., Claussen, N., Kriven W.M., Rühle, M.: Stability of tetragonal ZrO2 particles in ceramic matrices, J. Am. Ceram. Soc., 65, [12], 642 – 650, (1982).
6 Lange, F.F.: Transformation toughening, part 4: Fabrication, fracture toughness and strength of Al2O3 - ZrO2 composites, J. Mat. Sci., 17, 247 – 254, (1982).
7 Gregori, G., Burger, W., Sergo, V.: Piezo-spectroscopic analysis of the residual stresses in zirconia-toughened alumina ceramics: the influence of the Tetragonal-to-monoclinic transformation, Mater. Sci. Eng., A271, 401 – 406, (1999).
8 DeAza, A. Chevalier, J. Fantozzi, G., Schehl, M. Torrecillas, R: Slow-Crack-growth behavior of zirconia-toughened alumina ceramics processed by different methods, J. Am. Ceram. Soc., 86, [1], 115 – 20, (2003).
9 Patterson, A.L.: The scherrer formula for x-ray particle size determination, Phys. Rev., 56, 978 – 982, (1939).
10 Anstis, G. R., Chantikul, P., Lawn, B. R., Marshall, D. B. A.: A critical evaluation of indentation techniques for measuring fracture toughness. I. Direct crack measurements, J. Am. Ceram. Soc., 64, 533 – 538, (1981).
11 Chantikul, P., Anstis, G.R., Lawn, B.R., Marshall, D.B.A.: A critical evaluation of indentation techniques for measuring fracture Toughness. II. Strength method, J. Am. Ceram. Soc., 64, 539 – 543, (1981).
12 Toraya, H., Yoshimura, M., Somiya, S.: Calibration curve for quantitative analysis of the monoclinic-tetragonal ZrO2 system by x-ray diffraction, J. Am. Ceram. Soc., 67, [6], C119 – 121, (1984).
13 Mendelson, M.I.: Average grain size in polycrystalline ceramics, J. Am. Ceram. Soc., 52, 443, (1969).
14 Lange, F.F.: Transformation toughening, part 3: Experimental observations in the ZrO2-Y2O3 System, J. Mat. Sci., 17, 240 – 246, (1982).
15 Quinn G.D., Bradt R.C.: On the vickers indentation fracture toughness test, J. Am. Ceram. Soc., 90, [3], 673 – 680, (2007).
16 Kern, F: Properties of 2.5Y-TZP manufactured from alumina-doped yttria-coated pyrogenic zirconia nanopowder, J. Ceram. Sci. Tech., 2, [2], 89 – 96, (2011).
17 Kern, F: Microstructure and mechanical properties of hot-pressed alumina 5 vol% zirconia nanocomposites, J. Ceram. Sci. Tech., 2, [1], 69 – 74, (2011).
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