Superplastic Deformation of Zirconia/Alumina Composites Produced by Reaction Bonding
Reaction bonding of A12O3 (RBAO) has been developed recently at TUHH1 as an alternative to conventional processing of alumina ceramics. In this process, nanosized RBAO precursor powders are produced by attrition milling of Al/Al2O3 powder mixtures. During heat treatment in air at temperatures below 1000°C, the metal phase in RBAO compacts fully converts to nanometer sized oxide crystallites which bond the primary A12O3 particles. The volume-expansion (28%) associated with the Al→ A12O3 transition partially compensates for the sintering shrinkage occurring during further heat treatments at temperatures of 1200 – 1550°C. Incorporation of other metal or ceramic phases, exhibiting larger volume expansion upon oxidation, can be used to further compensate for the sintering shrinkage. In addition to its low-to-zero shrinkage capability, other attributes of the RBAO-process like low raw material costs, suitability for incorporating non-equiaxed second phases (platelets, fibers) and excellent green state machinability make this technique very attractive for high-performance applications.
KeywordsStress Exponent Uniaxial Compression Test Superplastic Flow Reaction Bonding Attrition Milling
Unable to display preview. Download preview PDF.
- 2.K. Okada and T. Sakuma, “Grain Growth Kinetics in ZrO2-dispersed A12O3 Ceramics”, Br. Cer. Trans., 93  (1994) 71–74.Google Scholar
- 5.D. Holz, S. Wu, S. Scheppokat and N. Claussen, “Effect of Processing Parameters on Phase and Microstructure Evolution in RBAO Ceramics”, J. Am. Ceram. Soc., accepted for publication.Google Scholar
- 8.F. Wakai, “Superplasticity of Zirconia Toughened Ceramics”, Thesis, Kyoto University, Japan, 1988.Google Scholar
- 10.Y. Oishi, K. Ando and Y. Sakka, “Lattice and Grain-Boundary Diffusion Coefficients of Cations in Stabilized Zirconia”, pp. 208-19 in Advances in Ceramics, Vol. 12, American Ceramic Society, 1983.Google Scholar