Q. Tai. A. Mocellin/Ceramics International 25(1999)395-408 omposites have been extensively studied [15, 25-40 Most studies on Al,Ox-ZrO, composites indicated Wakai and Kano [28]demonstrated that a 3 mol% yttria that the introduction of rO2 in Al2O3 made the creep stabilized zirconia with 27. 3 vol% alumina composite rate of the composites lower than that of either of their (3Y20A)was capable of large superplastic elongations single-phase constituents. [15, 27[30-39] Wakai et al of more than 200%, while Nieh et al. [29] reported a [27, 30] and Chen [39] attributed it to the suppression of tensile elongation of 500% at 1650C for 3Y20A. The interface reactions controlled diffusion creep of Al2O3 superplasticity of the Al2O3-ZrO2 composites has been or hindrance of grain-boundary movement by reported by many other ceramic workers granular ZrO2 particles. French et al. [15] indicated that Inspection of all the available data of the Al2O3-ZrO2 the decrease of the creep rate was caused by a strong composites shown in Table I indicates that the values of segregation of Yt(and possibly Zr*t) to the alumina n range from about 1. 5 to 2.5. The activation energies grain boundaries, which resulted in a decrease of AlO3 tend to lie in the range 600-700 KJ mol-I. The values of in grain boundary dislocation mobility and interface inverse grain size exponent were only reported by Wang reaction controlling diffusional creep rate. The effect of et al. [3l] and Owen et al. [23](p=3, for 5 vol% ZrO content on the creep rate of composites was first p=2. 1 for 3Y20A) The differences in the values of n, 2 studied by Wakai et al. [30, 38](Fig. 7). The results and p are probably caused by the conditions of test, the showed that when the ZrO2 content was more than different stress, strain rate and temperature ranges, the 14.3 vol% the creep rate decreased with decrease of the ZrO2 content, the levels of impurities, and the micro- ZrO2 content. The values of n remained almost structure of the composites unchanged. Recent investigations 35-37 Table 2 Deformation behaviours of Al2O3-based non-oxide ceramic particle or whisker dditive Content Test Atm. g ranges Grain size (vol %) type (MPa) (KJ mol-) Chokshi et al 40-10010-7-10 1500 Porter et al 40-20010-7-10-31450-1600 (1987)[42] Lipetzky et al. 30-25010=10-10-51200-1300 450-500 (1988)43 9.3,18B 40-20010-1-10-4/4 40-20010-710 (1988)[44 B 6.3 37-30010-910 1990)[45] De arellano.l 6-30 C argon,air100-30010-8-10-41300-1500 (1991)[47 BBBB 37-30010-910-6 Lipetzky et al. 25-25010-910 13040 269,655 (1991)[48 25-25010--10 210.966 14-1.7 (1992)[49] DeArellano-Lopez 91400 0.9-1.9 etal.(1993)[50 Sic wy 15-30C 8041010-6-10-40491400 2.4-5.9 10-10010-7-10-41400-1550 820-830 (1995)[51] 50-23010-810-7 12-8 1996)[52] Ohji et al 994)[53 Deng et al BBTBBB aaaa 50-23010-8-10-71300128 50-15010-10-1 1200-1300 40-12510-910-51160-1400<50.6 (1996)[54 40-12510-910-51160-1400 Katsumura et al CosNo.so)54 B argon50-30010-6-10-31300-1400081.42022-281.5 (1987)[55 TiCal T vacuum 7010-5-10-21300-1550 3.2-4.1 (1991)composites have been extensively studied [15, 25±40]. Wakai and Kano [28] demonstrated that a 3 mol% yttria stabilized zirconia with 27.3 vol% alumina composite (3Y20A) was capable of large superplastic elongations of more than 200%, while Nieh et al. [29] reported a tensile elongation of 500% at 1650C for 3Y20A. The superplasticity of the Al2O3-ZrO2 composites has been reported by many other ceramic workers. Inspection of all the available data of the Al2O3-ZrO2 composites shown in Table 1 indicates that the values of n range from about 1.5 to 2.5. The activation energies tend to lie in the range 600±700 KJ molÿ1 . The values of inverse grain size exponent were only reported by Wang et al. [31] and Owen et al. [23] (p=3, for 5 vol% ZrO2; p=2.1 for 3Y20A). The di€erences in the values of n, Q and p are probably caused by the conditions of test, the di€erent stress, strain rate and temperature ranges, the ZrO2 content, the levels of impurities, and the micro￾structure of the composites. Most studies on Al2O3-ZrO2 composites indicated that the introduction of ZrO2 in Al2O3 made the creep rate of the composites lower than that of either of their single-phase constituents. [15,27] [30±39] Wakai et al. [27,30] and Chen [39] attributed it to the suppression of interface reactions controlled di€usion creep of Al2O3 or hindrance of grain-boundary movement by inter￾granular ZrO2 particles. French et al. [15] indicated that the decrease of the creep rate was caused by a strong segregation of Y3+ (and possibly Zr4+) to the alumina grain boundaries, which resulted in a decrease of Al2O3 in grain boundary dislocation mobility and interface reaction controlling di€usional creep rate. The e€ect of ZrO2 content on the creep rate of composites was ®rst studied by Wakai et al. [30,38] (Fig. 7). The results showed that when the ZrO2 content was more than 14.3 vol% the creep rate decreased with decrease of the ZrO2 content. The values of n remained almost unchanged. Recent investigations [35±37] showed Table 2 Deformation behaviours of Al2O3-based non-oxide ceramic particle or whisker composites Reference Additive Content (vol%) Test type Atm.  ranges (MPa)  ranges (Sÿ1 ) T ( C) Grain size (m) Al2O3additive np Q (KJ molÿ1 ) Chokshi et al. (1985) [41] SiC(w)a 18 B air 40±100 10ÿ7 ±10ÿ4 1500 45 ± 5.2 ± ± Porter et al. (1987) [42] SiC(w) 5±20 B air 40±200 10ÿ7 ±10ÿ3 1450±1600 ± ± 5 ± 450 Lipetzky et al. (1988) [43] SiC(w) 33 B air 30±250 10ÿ10±10ÿ5 1200±1300 1±2 ± 1,5 ± 450±500 Xia et al. SiC(w) 9.3,18 B air 40±200 10ÿ7 ±10ÿ4 1400±1550 1±2 ± 3.8 ± ± (1988) [44] SiC(w) 30 B air 40±200 10ÿ7 ±10ÿ4 1400±1550 1±2 ± 6.3 ± ± Lin et al. SiC(w) 20 B air 37±300 10ÿ9 ±10ÿ5 1200±1400 2 ± 2 ± ± (1990) [45] SiC(w) 20 B air >125 10ÿ9 ±10ÿ5 1400 2 ± 7±8 ± ± DeArellano-Lopez et al. (1990) [46] SiC(w) 6±30 C argon, air 100±300 10ÿ8 ±10ÿ4 1300±1500 ± ± 1.2±1.8 ± 620 Lin et al. SiC(w) 30±50 B air 37±300 10ÿ9 ±10ÿ5 1300 1-2 ± 6 ± ± (1991) [47] SiC(w) 30±50 B air 37±300 10ÿ9 ±10ÿ5 1200 1-2 ± 3 ± ± SiC(w) 10 B air 37±300 10ÿ9 ±10ÿ6 1300 8 ± 4 ± ± SiC(w) 10 B air 37±300 10ÿ9 ±10ÿ6 1200 8 ± 2 ± ± Lipetzky et al. SiC(w) 33 C air 25±250 10ÿ9 ±10ÿ6 1200±1400 1±2 ± 1,3 ± 269, 655 (1991) [48] SiC(w) 33 C nitrogen 25±250 10ÿ9 ±10ÿ6 1200±1400 1±2 ± 1,3 ± 210, 966 Swan et al. (1992) [49] SiC(w) 30 C air 25±200 10ÿ8 ±10ÿ5 1200±1350 1±2 ± 1.4±1.7 ± 370 DeArellano-Lopez SiC(w) 5±30 C argon 10±240 10ÿ7 ±10ÿ5 0491400 ± ± 0.9±1.9 ± ± et al. (1993) [50] SiC(w) 15±30 C argon 80±410 10ÿ6 ±10ÿ4 0491400 ± ± 2.4±5.9 ± ± Xia et al. (1995) [51] SiC(w) 9.3 B air 10±100 10ÿ7 ±10ÿ4 1400±1550 1±2 ± 3.8 ± 820±830 Lin et al. SiC(w) 10 B air 50±230 10ÿ8 ±10ÿ7 1200 1.2±8 ± 2 1 ± (1996) [52] SiC(w) 10 B air 50±230 10ÿ8 ±10ÿ7 1300 1.2±8 ± 3.5 ± ± Ohji et al. SiC(p) 17 T air 50±150 10ÿ10±10ÿ7 1200±1300 2 0.1 3.1 ± ± (1994) [53] SiC(p) 17 B air 100±200 10ÿ11±10ÿ9 1200 2 0.1 2.2 ± ± Deng et al. SiC(p) 10 B air 40±125 10ÿ9 ±10ÿ5 1160±1400 <5 0.6 4.27 ± 444 (1996) [54] SiC(p) 10 B air 40±125 10ÿ9 ±10ÿ5 1160±1400 55 2.7 4.75 ± 666 Katsumura et al. (1987) [55] TiC0.5N0.5(p) 54 B argon 50±300 10ÿ6 ±10ÿ3 1300±1400 0.8 1.4 2.0±2.2 ± 281.5 Nagano et al. (1991) [56] TiC(p) 26 T vacuum 8±70 10ÿ5 ±10ÿ2 1300±1550 1.2Ä 3.2±4.1 ± 853 a : (w)=whiskers, (p)=particles 400 Q. Tai. A. Mocellin / Ceramics International 25 (1999) 395±408