on the physical and chemical properties of reinforcing grain growth or cavitation. Fridez [21] has reported particles or whiskers, their content, morphologies and that creep deformation accelerated grain growth. The distributions, and microstructures of composites change in the crystallographic texture of alumina was including grain sizes and shapes, pores, grain bound observed at higher stress range. [21, 23] The main defor aries, interfaces, as well as stress and temperature. Dur- mation mechanisms were diffusional creep, grain ing deformation, there often occur microstructural boundary sliding and sometimes basal slip. The diffu changes such as grain growth, changes of grain shape sional creep can become inter rface-controlled at low (grain elongation), texture development, formation of stresses, causing non-Newtonian creep behaviour. The ntermediate or intergranular phase, dislocation activity, cavitation was often caused by unaccommodated GBS vacancy nucleation and evolution, cavitation and evo- or basal slip and the basal slip can give rise to a defor ution, formation and development of microcracks, etc. mation texture creep deformation is an essential aspect which li The study of such microstructural changes accompar In Al2O3-based ceramic particle or whisker compo- sites, the creep behaviours of Al2O3-ZrO2 and Al_O3 ortant foundation for analysing creep deformation SiC composites have been most extensively investigated behaviours and creep mechanisms of composites In the following the creep behaviours of Al2O3-based we will first recall briefly the high oxide ceramic composites and Al2O3-based nonoxide temperature deformation behaviours of fine-grained ceramic composites will be discussed. The correspond- alumina and then review the high temperature defor- ing experimental data produced during the past 10 years mation behaviours of Al2O3-based ceramic composites. or so in both families of materials are summarised in High temperature deformation behaviours of fine- Tables I and 2, respectively grained alumina were widely investigated. [5-9][18-23] Most authors have shown that n=1-2, P=2-3, and 3. 1. Al2O3-based oxide ceramic particle composites 0=430-500 KJ mol- can represent deformation data at lower stress range. The stress exponent generally 3. 1.1. A1203-ZrOz composites decreased with increasing grain size. In some studies. Since Wakai et al. reported that a 3 mol% yttria stabi- non-steady state deformation has been reported due to lized zirconia exhibited superplasticity [24, Al2O3-ZrO Table l Deformation behaviours of Al2O3-based oxide ceramic particle composites Reference Additive Content Test Atm. a ranges e ranges T(C) Grain size (um) n p Q (vol%) type (MPa) (S-) AlO3 additiv KJ mol-) Wakai et al Zro 72.7C 10=4-10-31400-1500 Kellett et a ZrO,20Cair30-10010-4-10-21500 0.72.1 Wakai et al.(1988)[27 14.3Tair10-10010-8-10-51250-1450100.51.7-2.1 Wakai et al. (1988)[28 ZrO,727Tair10-14010-7-10-51250-14500.50.52.1 590-600 Nieh et al.(1989)[29] ZrO,72.7 r vacuun54010-5-10-21450-1650 ~0.5b Wakai et al.(1989)[301 ZrO, Tair2-10010-7-10-31250-14500.60.521-24-720-780 ZrO230.8Tair2-10010-7-10-31250-14501.00.619-24-680-740 ZrO314.3Tair2-10010-7-10-31250-14501.0 0.5172.1 540-760 Wang et al. (1991)B31 ZrO 5 C argon5-20010-5-10-41400-150028 3630 HfO25 C argon5-20010-510-41400-150027 5 C argon5-6010--10-41400-15003.8 Owen et al. (1994)[32] 7 T 4-10010-8-10-31327-14770.4 0.42.82.1 French et al. (1994)[15] TZZY 50Tair35-7510-810-61200-1350 air35-7510-810-71210-1350 Calderon-Mereno et al. (1995)[33] ZrO2 5.5C 0-15010-8-10-41300-145047 14 Calderon-Mereno et al. (1995)[33 ZrO2 5.5Cair10-15010-810-41300145026<1 Chevalier et al. (1997)[34 ZrO, 10B Bair50-20010-810-6120014002 0.5 760 Calderon-Mereno(1997)[35] 40Cair45-8510-510-41400-15002.31.61.7 Calderon-Mereno(1997)[35] Zro 649510-5-10 Calderon-Mereno(1997)[35] Zro 10Cair70-12310-5-10-415002 Flacher et al.(1997)[36 ZrO,5-20Cair20-13010-5-10-41300-14000.2 Clarisse et al. (1997)[3 ZrO, 0Cair4-20010-6-10-31275-14000.640.551-2 640-705 Clarisse et al. (1997)[37 ZrO2380Cair420010-7-10-31275-14001.120.801-2 Clarisse et al. (1997)[37] ZrO2380Cair420010-7-10-41275-14001 0.711-2 663-715 Duong et al. ( 1993)[16 YAG50Cair3-2010-8-10-51400-150010 612 YAG 3-2010-8-10-51400-15008 592 compression, T=tension, B=bendin Average grainon the physical and chemical properties of reinforcing particles or whiskers, their content, morphologies and distributions, and microstructures of composites including grain sizes and shapes, pores, grain bound￾aries, interfaces, as well as stress and temperature. Dur￾ing deformation, there often occur microstructural changes such as grain growth, changes of grain shape (grain elongation), texture development, formation of intermediate or intergranular phase, dislocation activity, vacancy nucleation and evolution, cavitation and evo￾lution, formation and development of microcracks, etc. The study of such microstructural changes accompany￾ing creep deformation is an essential aspect which is an important foundation for analysing creep deformation behaviours and creep mechanisms of composites. In this chapter, we will ®rst recall brie¯y the high temperature deformation behaviours of ®ne-grained alumina and then review the high temperature defor￾mation behaviours of Al2O3-based ceramic composites. High temperature deformation behaviours of ®ne￾grained alumina were widely investigated. [5±9] [18±23] Most authors have shown that n=1±2, p=2±3, and Q=430±500 KJ molÿ1 can represent deformation data at lower stress range. The stress exponent generally decreased with increasing grain size. In some studies, non-steady state deformation has been reported due to grain growth or cavitation. Fridez [21] has reported that creep deformation accelerated grain growth. The change in the crystallographic texture of alumina was observed at higher stress range. [21,23] The main defor￾mation mechanisms were di€usional creep, grain boundary sliding and sometimes basal slip. The di€u￾sional creep can become interface-controlled at low stresses, causing non-Newtonian creep behaviour. The cavitation was often caused by unaccommodated GBS or basal slip and the basal slip can give rise to a defor￾mation texture. In Al2O3-based ceramic particle or whisker compo￾sites, the creep behaviours of Al2O3-ZrO2 and Al2O3- SiC composites have been most extensively investigated. In the following the creep behaviours of Al2O3-based oxide ceramic composites and Al2O3-based nonoxide ceramic composites will be discussed. The correspond￾ing experimental data produced during the past 10 years or so in both families of materials are summarised in Tables 1 and 2, respectively. 3.1. Al2O3-based oxide ceramic particle composites 3.1.1. Al2O3-ZrO2 composites Since Wakai et al. reported that a 3 mol% yttria stabi￾lized zirconia exhibited superplasticity [24], Al2O3-ZrO2 Table 1 Deformation behaviours of Al2O3-based oxide ceramic particle composites Reference Additive Content (vol%) Test type a Atm.  ranges (MPa)  ranges (Sÿ1 ) T ( C) Grain size (m) Al2O3 additive np Q (KJ molÿ1 ) Wakai et al. (1986) [25] ZrO2 72.7 C air ± 10ÿ4 ±10ÿ3 1400±1500 ± ± 1.2±2.0 ± 620 Kellett et al. (1986) [26] ZrO2 20 C air 30±100 10ÿ4 ±10ÿ2 1500 1.1 0.7 2.1 ± ± Wakai et al. (1988) [27] ZrO2 14.3 T air 10±100 10ÿ8 ±10ÿ5 1250±1450 1.0 0.5 1.7±2.1 ± 750 Wakai et al. (1988) [28] ZrO2 72.7 T air 10±140 10ÿ7 ±10ÿ5 1250±1450 0.5 0.5 2.1 ± 590±600 Nieh et al. (1989) [29] ZrO2 72.7 T vacuum 5±40 10ÿ5 ±10ÿ2 1450±1650 0.5b 2± ± Wakai et al. (1989) [30] ZrO2 50 T air 2±100 10ÿ7 ±10ÿ3 1250±1450 0.6 0.5 2.1±2.4 ± 720±780 ZrO2 30.8 T air 2±100 10ÿ7 ±10ÿ3 1250±1450 1.0 0.6 1.9±2.4 ± 680±740 ZrO2 14.3 T air 2±100 10ÿ7 ±10ÿ3 1250±1450 1.0 0.5 1.7±2.1 ± 640±760 Wang et al. (1991) [31] ZrO2 5 C argon 5±200 10ÿ5 ±10ÿ4 1400±1500 2.8 ± ± 3 630 HfO2 5 C argon 5±200 10ÿ5 ±10ÿ4 1400±1500 2.7 ± ± 3 685 TiO2 5 C argon 5±60 10ÿ5 ±10ÿ4 1400±1500 3.8 ± ± 2 570 Owen et al. (1994) [32] ZrO2 72.7 T air 4±100 10ÿ8 ±10ÿ3 1327±1477 0.4 0.4 2.8 2.1 585 French et al. (1994) [15] ZrO2 50 T air 35±75 10ÿ8 ±10ÿ6 1200±1350 2.3 1.8 ± 633 YAG 50 T air 35±75 10ÿ8 ±10ÿ7 1210±1350 2.0 2.6 ± 695 Calderon-Mereno et al. (1995) [33] ZrO2 5.5 C air 10±150 10ÿ8 ±10ÿ4 1300±1450 4.7 ± 1.4 ± 580 Calderon-Mereno et al. (1995) [33] ZrO2 5.5 C air 10±150 10ÿ8 ±10ÿ4 1300±1450 2.6 <1 1.8 ± 540 Chevalier et al. (1997) [34] ZrO2 10 B air 50±200 10ÿ8 ±10ÿ6 1200±1400 2 0.5 2.5 ± 760 Calderon-Mereno (1997) [35] ZrO2 40 C air 45±85 10ÿ5 ±10ÿ4 1400±1500 2.3 1.6 1.7 ± ± Calderon-Mereno (1997) [35] ZrO2 20 C air 64±95 10ÿ5 ±10ÿ4 1500 2.3 1.6 1.4 ± ± Calderon-Mereno (1997) [35] ZrO2 10 C air 70±123 10ÿ5 ±10ÿ4 1500 2.3 1.6 1.2 ± ± Flacher et al. (1997) [36] ZrO2 5±20 C air 20±130 10ÿ5 ±10ÿ4 1300±1400 0.2Ä 2 ± 650 Clarisse et al. (1997) [37] ZrO2 80 C air 4±200 10ÿ6 ±10ÿ3 1275±1400 0.64 0.55 1±2 ± 640±705 Clarisse et al. (1997) [37] ZrO2 80 C air 4±200 10ÿ7 ±10ÿ3 1275±1400 1.12 0.80 1±2 ± 642±723 Clarisse et al. (1997) [37] ZrO2 80 C air 4±200 10ÿ7 ±10ÿ4 1275±1400 1.40 0.71 1±2 ± 663±715 Duong et al. (1993) [16] YAG 50 C air 3±20 10ÿ8 ±10ÿ5 1400±1500 10 3 1.1 ± 612 YAG 75 C air 3±20 10ÿ8 ±10ÿ5 1400±1500 8 3 1.1 ± 592 a C=compression, T=tension, B=bending. b Average grain size. Q. Tai. A. Mocellin / Ceramics International 25 (1999) 395±408 399