Q. Tai. A. Mocellin/Ceramics International 25(1999)395-408 In the Al,O3-based oxide ceramic particle composites, Ibi. Liu, Unsteady diffusional creep of a dual- I2OZrO2 composites have been extensively investi phase material, Scripta Mater. 36( 1997)1081-1087 gated. The addition of Zro2 in Al2O3 makes the creep 5 W.R. Cannon, O.D. Sherby, Creep behaviours and grain bound- resistance of the composites superior to either of their ry sliding in polycrystalline Al2O3: Journal of the American single-phase constituents. In certain conditions, the 6 C K. Davies, Ray S.F. Sinha, High temperature creep deforma- creep rate increases with increasing the zrO2 content tion of polycrystalline alumina in tension, in: P. Popper, (Ed ) The impurities such as Si, Fe, Na at grain boundaries Special Ceramics 5, British Ceramic Research Association, Stoke favour grain boundary sliding, thus increasing the creer on Trent, UK, 1972, pp 193-209 rate. The effect of Yt or Mg on the creep rate of the E.M. Passmore, T. Vassilos, Creep of dense, pure, fine grained aluminium oxide, Journal of the American Ceramics Society 49 AlOrZro2 composites is ambiguous and needs to be further investigated. Microstructures of deformed spe- [8] A.H. Chokshi, J.R. Porter, High temperature mechanical prop- imens of Al2O - ZrO2 composites show considerable rties of single phase alumina, Journal Mater. Sci. 21(1986)705- stability. The main creep mechanism of Al2O3-ZrO2 [9)AH. Heuer, N.J. Tighe, R.M. Cannon, Plastic deformation of composites is grain boundary sliding and grain rearran Basal slip and gement accommodated grain-boundary sliding, Journal of the American Other Al2O3-based oxide ceramic pa e comi Ceramics Society 63(1980)53-58. uch as Al2OrY3AlsO12 composite show an excellent 10]J. P. Poirier, in: P H. Cook, W.B. Harland, N F. Hughes, A. Put- creep resistance. However, they are less documented nis,JG. Sclater, M.R.A. Thomson(Eds ) Cambridge University and need more investigation. Press, Cambridge, 1985, pp. 194-212. [1] D.R. Clarke, High temperature deformation of a polycrystalline In the Al2O3-based nonoxide ceramic particle or umina containing an intergranular glassy phase, Journal Mater whisker composites, most studies concentrate on Al2O3- Sci.20(1985)1321-1332. Sic composites, especially Al2O3-SiC(). The introduc [2]AH. Chokshi, T.G. Langdon, Characteristics of creep deforma tion in ceramics, Mater. Sci. Technol. 7(1991)577-58 tion of SiC into Al203 strongly increases the creep [13] M.F. Ashby, A first report on deformation-mechanism maps, resistance of the material. Higher temperatures and Acta Metall20(1972)887-897 higher stresses often result in extensive cavitation and [14 F.A. Mohamed, T.G. Langdon, Deformation mechanism maps microcracks in Al2O3-SiC(w) composites, increasing based on grain size, Metall. Trans. 5(1974) heir creep rate and resulting in a higher stress sensi- [5] J.D. French, J. Zhao, M.P. Harmer, H.M. .A. Miller tivity In air ambient, the oxidation of Sic whiskers or Creep of duplex microstructures, Journal of the American Cera- particles may greatly decrease the creep resistance. The Society771994)2857-2865 [6 H. Duong, J. Wolfenstine, Creep behaviour of fine-grained two. main creep mechanism of the Al2O3-SiC composites is phase Al2Or-Y3Al5O12 materials, Mater. Sci. Eng. A. Al72 ain boundary sliding partially accommodated by dif- (1993)173-179. fusion. In some conditions the deformation may [7 I.w. Chen, A.S. Argon, Steady state power-low creep in hetero- controlled by a creep cavitation and microcracking geneous alloys with coarse microstructures, Acta Metall. 27 mechanism or even by a dislocation creep mechanism (1979)758791 [18 E Herve, R. Dendievel, G. Bonnet, Steady-state power-low creep Other Al2O3-based nonoxide ceramic composites, in inclusion matrix composite materials, Acta Metall. Mater. 43 such as Al,OrTiC, Al,O -TiC NIr AlO3-TiN com- (1995)40274034 posite have been less investigated. During deformation [19R. M. Canon, W.H. Rhodes, A H. Heuer, Plastic deformation of of those composites, the existence of T1O or T1,O3 at fine-grained alumina(Al2O3 1, Interface-controlled diffusional grain boundaries or interfaces introduced by additives Ror reep, Journal of the American Ceramics Society 63(1980)46-53. 20]AH. Chokshi, J.R. Porter, Analysis of concurrent grain growth or formed by the reaction between Al2O3 and additives during creep of polycrystalline alumina, Journal of the American during the deformation deteriorates the high tempera- Ceramics Society 69(1986)C37. ture strength and the creep resistance of the composites 21]J D. Fridez, Etude structurale de la deformation superplastique Avoiding or controlling the existence of TiO, or Ti2O3 d'une alumine dense a grains fins. Ph. D thesis, EPFL, Lausanne, Switzerland. 1987. at grain boundaries or interfaces during the deforma- [22 L.A. Xue, I.W. Chen, Deformation and grain growth of low- tion will be an Important future issue in this kind of tered high-purity alumina, Journal of the Amer- composit 23 P. Gruffel, Evolutions structurales d alumine a grains fins dopes a Yttrium etfluage superplastique. Ph. D. thesis, EPFL,Lau- sanne. Switzerland. 1991 References 24 F. Wakai, S Sakaguchi, Y. Matsuno, Superplasticity of yttria ilized tetragonal ZrO2 polycrystals Y-TZP) Ad [R. Raj, M.F. Ashby, On grain boundary sliding and diffusional Mater.l(1986)25926 creep, Metall. Trans. 2(1971)1113-1127 25 F. Wakai, H. Kato, S. Sagaguchi, Compressive deformation of 2I.w. Chen, Superplastic ceramic composites, Ceram. Trans. 19 Y2O3-stabilized ZrO2/Al2O3 composite, Yogyo Kyokaishi 9 (1991)695-706 (19861027-1030 3K.S. Ravichandran, V. Seetharaman, Prediction of steady state [26 B.J. Kellett, FF. Lange, Hot forging characteristics of fine. creep behaviour of two phase composites. Acta Metall. Mater. 41 grained ZrO2 and Al2O3/ZrO2 ceramics, Journal of the American (1993)3351-336 Ceramics Society 69(1986)C172In the Al2O3-based oxide ceramic particle composites, Al2O3±ZrO2 composites have been extensively investi￾gated. The addition of ZrO2 in Al2O3 makes the creep resistance of the composites superior to either of their single-phase constituents. In certain conditions, the creep rate increases with increasing the ZrO2 content. The impurities such as Si, Fe, Na at grain boundaries favour grain boundary sliding, thus increasing the creep rate. The e€ect of Y3+ or Mg2+ on the creep rate of the Al2O3±ZrO2 composites is ambiguous and needs to be further investigated. Microstructures of deformed spe￾cimens of Al2O3±ZrO2 composites show considerable stability. The main creep mechanism of Al2O3±ZrO2 composites is grain boundary sliding and grain rearran￾gement. Other Al2O3-based oxide ceramic particle composites such as Al2O3±Y3Al5O12 composite show an excellent creep resistance. However, they are less documented and need more investigation. In the Al2O3-based nonoxide ceramic particle or whisker composites, most studies concentrate on Al2O3± SiC composites, especially Al2O3±SiC(w). The introduc￾tion of SiC into Al2O3 strongly increases the creep resistance of the material. Higher temperatures and higher stresses often result in extensive cavitation and microcracks in Al2O3-SiC(w) composites, increasing their creep rate and resulting in a higher stress sensi￾tivity. In air ambient, the oxidation of SiC whiskers or particles may greatly decrease the creep resistance. The main creep mechanism of the Al2O3-SiC composites is grain boundary sliding partially accommodated by dif￾fusion. In some conditions the deformation may be controlled by a creep cavitation and microcracking mechanism or even by a dislocation creep mechanism. Other Al2O3-based nonoxide ceramic composites, such as Al2O3±TiC, Al2O3±TiCxN1-x, Al2O3-TiN com￾posite have been less investigated. During deformation of those composites, the existence of TiO2 or Ti2O3 at grain boundaries or interfaces introduced by additives or formed by the reaction between Al2O3 and additives during the deformation deteriorates the high tempera￾ture strength and the creep resistance of the composites. Avoiding or controlling the existence of TiO2 or Ti2O3 at grain boundaries or interfaces during the deforma￾tion will be an important future issue in this kind of composites. References [1] R. Raj, M.F. Ashby, On grain boundary sliding and di€usional creep, Metall. Trans. 2 (1971) 1113±1127. [2] I.W. Chen, Superplastic ceramic composites, Ceram. Trans. 19 (1991) 695±706. [3] K.S. Ravichandran, V. Seetharaman, Prediction of steady state creep behaviour of two phase composites, Acta Metall. Mater. 41 (1993) 3351±3361. [4] K. Wakashima, Fubi. Liu, Unsteady di€usional creep of a dual￾phase material, Scripta Mater. 36 (1997) 1081±1087. [5] W.R. Cannon, O.D. Sherby, Creep behaviours and grain bound￾ary sliding in polycrystalline Al2O3: Journal of the American Ceramics Society 60 (1977) 44±47. [6] C.K. Davies, Ray S.F. Sinha, High temperature creep deforma￾tion of polycrystalline alumina in tension, in: P. Popper, (Ed.), Special Ceramics 5, British Ceramic Research Association, Stoke on Trent, UK, 1972, pp. 193±209. [7] E.M. Passmore, T. Vassilos, Creep of dense, pure, ®ne grained aluminium oxide, Journal of the American Ceramics Society 49 (1966) 166±168. [8] A.H. Chokshi, J.R. Porter, High temperature mechanical prop￾erties of single phase alumina, Journal Mater. Sci. 21 (1986) 705± 710. [9] A.H. Heuer, N.J. Tighe, R.M. Cannon, Plastic deformation of ®ne-grained alumina (Al2O3): II. Basal slip and non￾accommodated grain-boundary sliding, Journal of the American Ceramics Society 63 (1980) 53±58. [10] J.P. Poirier, in: P.H. Cook, W.B. Harland, N.F. Hughes, A. Put￾nis, J.G. Sclater, M.R.A. Thomson (Eds.), Cambridge University Press, Cambridge, 1985, pp. 194±212. [11] D.R. Clarke, High temperature deformation of a polycrystalline alumina containing an intergranular glassy phase, Journal Mater. Sci. 20 (1985) 1321±1332. [12] A.H. Chokshi, T.G. Langdon, Characteristics of creep deforma￾tion in ceramics, Mater. Sci. Technol. 7 (1991) 577±584. [13] M.F. Ashby, A ®rst report on deformation-mechanism maps, Acta Metall. 20 (1972) 887±897. [14] F.A. Mohamed, T.G. Langdon, Deformation mechanism maps based on grain size, Metall. Trans. 5 (1974) 2339±2345. [15] J.D. French, J. Zhao, M.P. Harmer, H.M. Chan, G.A. Miller, Creep of duplex microstructures, Journal of the American Cera￾mics Society 77 (1994) 2857±2865. [16] H. Duong, J. Wolfenstine, Creep behaviour of ®ne-grained two￾phase Al2O3±Y3Al5O12 materials, Mater. Sci. Eng. A. A172 (1993) 173±179. [17] I.W. Chen, A.S. Argon, Steady state power-low creep in hetero￾geneous alloys with coarse microstructures, Acta Metall. 27 (1979) 758±791. [18] E. Herve, R. Dendievel, G. Bonnet, Steady-state power-low creep in inclusion matrix composite materials, Acta Metall. Mater. 43 (1995) 4027±4034. [19] R.M. Canon, W.H. Rhodes, A.H. Heuer, Plastic deformation of ®ne-grained alumina (Al2O3): 1, Interface-controlled di€usional creep, Journal of the American Ceramics Society 63 (1980) 46±53. [20] A.H. Chokshi, J.R. Porter, Analysis of concurrent grain growth during creep of polycrystalline alumina, Journal of the American Ceramics Society 69 (1986) C37. [21] J.D. Fridez, Etude structurale de la deÂformation superplastique d'une alumine dense aÁ grains ®ns. Ph. D. thesis, EPFL, Lausanne, Switzerland, 1987. [22] L.A. Xue, I.W. Chen, Deformation and grain growth of low￾temperature-sintered high-purity alumina, Journal of the Amer￾ican Ceramics Society 73 (1990) 3518±3521. [23] P. Gru€el, Evolutions structurales d'alumine aÁ grains ®ns dopeÂes aÁ l'yttrium et¯uage superplastique. Ph. D. thesis, EPFL, Lau￾sanne, Switzerland, 1991. [24] F. Wakai, S. Sakaguchi, Y. Matsuno, Suplerplasticity of yttria￾stabilized tetragonal ZrO2 polycrystals [Y-TZP], Adv. Ceram. Mater. 1 (1986) 259±263. [25] F. Wakai, H. Kato, S. Sagaguchi, Compressive deformation of Y2O3-stabilized ZrO2/Al2O3 composite, Yogyo Kyokaishi 94 (1986) 1027±1030. [26] B.J. Kellett, F.F. Lange, Hot forging characteristics of ®ne￾grained ZrO2 and Al2O3/ZrO2 ceramics, Journal of the American Ceramics Society 69 (1986) C172. Q. Tai. A. Mocellin / Ceramics International 25 (1999) 395±408 407