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2146 Journal of the American Ceramic Sociery-Takahashi et al. VoL 86. No. 12 References e Heat-treated smooth specimens A As cracked(2c=100um) AL2O, SiC Com 124-34 in Proceedings of the Intemational. Strong a Crack-healed at 1300C for Ih in air Adranced mater 2 K. MIhara.“N 1400 ial Issue of the Ceramics Society of Japan), J. Ceram. Soc. Jpn, 99 [10] -82(1991) BJ. Zhao, L C. Stearns, M. P. Harmer, H M. Chan, and G.A. Miller,"Mechanical 12 Behavior of Alumina-Silicon"Nanocomposites,JAm Ceram Soc., 76[21503-l (1993). P F. Becher and G. C. Wei, "Toughening Behavior in SiC-Whisker-Reinforced 1000 Cmm如300 Enforced tcfa- 800 Matrix Composite: Effect of Whisker Surface Treatment on Fracture Toughness, J.Am. Ceram.Soc,73[2]394-402(1990 E. E. Kim and A. J. Moorhead. "Oxidation Behavior and Effects of Oxidati 0600 the Strength of Sic-whisker Reinforced Alumina,J. Mater. Sci., 29, 1656-61 △ F. F. Lange and K. C. Radford, "Healing of Surface Cracks in Polycrystalli 曰400 AL2O3,"JAm. Ceram.Soc,53[0-11420-21(1970) "T.K. Gupta, "Crack Healing and Strengthening of Thermally Shocked Alumina, 200 AloU M. Thompson, H, M. Chan, M. P, Harmer, an nd Stress Relaxation in Al2OrSiC " Nanocomposites,J. Am. Ceram. Soc 78 31 56771(195 J E. Moffatt, W.J. Plumbridge, and R, Hermann, "High Temperature Cr and Alumina-SiC Composite, R.T 400 800 1200 1600 121.A Chou, H.M. Chan, and M P Harmer, "Effect of Annealing Environment Br. Cera Trans., 95 [123-29(1996). Test Temperature (C on the Crack Healing and Mechanical Behavior of Silicon Carbide-Reinforced nocomposites,J.An. Ceram. Soc., 81 [5] 1203-208(1998). J Petrovic and L. A Jacobson, " Controlled Surface Flaws in Hot-Pressed SiC, healed zone Soc,59|-2]34-37(1976 hoi and V. Tikare. "Crack Healing Behavior of Hot Pressed Silicon 16M. C. Chu, S. Sato, Y. Kobayashi, and K. Ando, " Damage Healing and h in air. The solid triangles show o of the crack-healed cole mens. The oB of the crack-healed specimens is almost mWmx1sm如0cmaa 7K. Ando, T Ikeda, S. Sato, F, Yao, and Y Kobayashi, "A Preliminary Study on above 1 C and decreases with increasing testing temperature Crack Healing Behaviour of SiaN /SiC Composite Ceramics, Fatigue Fract. Eng. up to 1300.C. Thus, the limit temperature for bending strength is Mater. Struct, 21 [1]119-22(1998) 1100 C. In Fig 4. the solid line indicates the bending strength of IsY. H. Zhang, L. Edwards, and W. J. Plumbridge, "Crack Healing in a Nitride Ceramics,J. Am. Ceram Soc., 81[7 34-37(1998) monolithic Al, O,AL,O,/SiC-W showed on considerably higher 19K. Ando, M. C. Chu, S. Sato, F. Yao, and Y,. Kobayashi, "The Stu than that of monolithic AL,O, in the entire temperature range Healing Behavior of Silicon Nitride Ceramics"(in Jpn ),Jpn. Soc. Mech. tested 623]1936-42(1998) IV. Conclusions 897-903(1999 2K. Ando, M. C, Chu, Y Kobayashi, F. Yao, and S. Sato, "Crack Healing AL,O, reinforced by SiC whiskers(Al203/SiC-w) was hot- Soc. Mech. Eng, 65 (633)1132-39(1999) pressed to investigate the crack-healing behavior. Semielliptical 22K. Ando, K. Tsuji, T. Hirasawa, Y Kobayashi, M. C. Chu, and SSato,Crack urface cracks of 100 um in surface length were introduced on each specimen. These specimens were crack-healed, and their ics"(in Jpn ),J. Soc. Mater. Sci. Jpn, 485]484-94(1999). strength was measured by a three-point bending test at room 2Y. Korous, M. C. Chu, M. Nakatani, and K. Ando, "Crack Healing Behavior of temperature and at elevated temperatures between 400 and SiC Ceramics, J. Am. Ceram Soc., 83[1n2788-92(2000) F. Yao, K. Ando, M. C. Chu, and S. Sato, "Crack-Healing Behavior, High- 1300C. The crack-healing behavior was studied as a function Temperature and Fa strength of Sic-Reinforced Silicon Nitride Composite, of healing temperature. The main conclusions obtained are as J Mater. Sci. Left, 19[ 12]1081-83(2000). follows K. Ando, K. Tsuji, M. Ariga, and S Sato, "Fatigue Strength Properties of Crack 1) The average values of Kic for Al,O,/SiC-W evalua Healed Mullite/SiC Composite Ceramics"(in Jpn ),J. Soc. Mater. Sci Jpn, 48 [10] the SEPB and the IF method were Kic= 5.7+ 1173-78(1999 5.6±0.2 espectively. The value of Kicfor F. Yao, K. Ando, M. C. Chu, and S Sato, "Static and Cyclic Fatigue Behaviour of Crack-Healed Si, N//SiC Composite Ceramics, J. Eur. Ceram Soc., 21, 991-9 than that of monolithic alumina (K 2001) MPam). Thus, as expected, the SiC whiskers also made their "Crack-Healing Behavior under Stress of Mullite/Silicon Carbide Ceramics and the AlO/SiC-W exhibited very interesting crack-healing Resultant Fatigue Strength, J.Am. Ceram Soc., 84[9]2073-78(2001). havior. The cracks with surface length 2c= 100 Hm could b 2K. Ando, M. C. Chu, K. Tsuji, T. Hirasawa, Y. Kobayashi, and S. Sato, "Crack Healing Behavior of Mullite/SiC Composite Ceramics, J. Eur. Ceram. Soc. healed by crack-healing at 1200 or 1300C for I h in air However, the surface cracks could not be healed completely below 2K. Ando, K Houjyou, M. C. Chu, S. Takeshita, K.Takahashi, S. Sakamoto, and the healing temperature of 1100C S. Sato, " Crack-Healing Behavior of Si3N,/SiC (3 The limit temperature for the bending sti healed specimens of Al,O/ SiC-w is 1.C strength of Al2O/SiC-W at elevated temperature is K. Takahashi, S Nakayama, and S Saito, "Crack-Healing Behavior of Mics under Cyclic Stress and Resultant Fatigue Strength at the than that of monolithic Al,O3 Healing Temperature, J Anm Ceram Soc., 85 [9]2268-72(2002)for 1 h in air. The solid triangles show B of the crack-healed specimens. The B of the crack-healed specimens is almost constant up to 1000°C. However, it shows a sudden decrease above 1100°C and decreases with increasing testing temperature up to 1300°C. Thus, the limit temperature for bending strength is 1100°C. In Fig. 4, the solid line indicates the bending strength of monolithic Al2O3 13 Al2O3/SiC-W showed B considerably higher than that of monolithic Al2O3 in the entire temperature range tested. IV. Conclusions Al2O3 reinforced by SiC whiskers (Al2O3/SiC-W) was hotpressed to investigate the crack-healing behavior. Semielliptical surface cracks of 100 m in surface length were introduced on each specimen. These specimens were crack-healed, and their strength was measured by a three-point bending test at room temperature and at elevated temperatures between 400° and 1300°C. The crack-healing behavior was studied as a function of healing temperature. The main conclusions obtained are as follows. (1) The average values of KIC for Al2O3/SiC-W evaluated by the SEPB method and the IF method were KIC 5.7 0.2 and 5.6 0.2 MPam1/2, respectively. The value of KIC for Al2O3/ SiC-W is larger than that of monolithic alumina (KIC 3–4 MPam1/2). Thus, as expected, the SiC whiskers also made their Al2O3 tougher. (2) Al2O3/SiC-W exhibited very interesting crack-healing behavior. The cracks with surface length 2c 100 m could be healed by crack-healing at 1200° or 1300°C for 1 h in air. However, the surface cracks could not be healed completely below the healing temperature of 1100°C. (3) The limit temperature for the bending strength of crackhealed specimens of Al2O3/SiC-W is 1100°C. The bending strength of Al2O3/SiC-W at elevated temperature is much higher than that of monolithic Al2O3. References 1 K. Niihara, A. Nakahira, G. Sasaki, and M. Hirabayashi, “Development of Strong Al2O3/SiC Composites”; pp. 124–34 in Proceedings of the International Meeting on Advanced Materials, Vol. 4. Materials Research Society, Tokyo, Japan, 1989. 2 K. Niihara, “New Design Concept of Structural Ceramics Nanocomposites” (The Centennial Issue of the Ceramics Society of Japan), J. Ceram. Soc. Jpn., 99 [10] 974–82(1991). 3 J. Zhao, L. C. Stearns, M. P. Harmer, H. M. Chan, and G. A. Miller, “Mechanical Behavior of Alumina–Silicon ‘Nanocomposites’,” J. Am. Ceram. Soc., 76 [2] 503–10 (1993). 4 P. F. Becher and G. C. Wei, “Toughening Behavior in SiC-Whisker-Reinforced Alumina,” J. Am. Ceram. Soc., 67 [12] C267–C269 (1984). 5 G. C. Wei and P. F. Becher, “Development of SiC-Whisker-Reinforced Ceramics,” Am. Ceram. Soc. Bull., 64 [2] 298–304 (1985). 6 J. Homeny, W. L. Vaughn, and M. K. Ferber, “Silicon Carbide Whisker/Alumina Matrix Composite: Effect of Whisker Surface Treatment on Fracture Toughness,” J. Am. Ceram. Soc., 73 [2] 394–402 (1990). 7 H. E. E. Kim and A. J. Moorhead, “Oxidation Behavior and Effects of Oxidation on the Strength of SiC-Whisker Reinforced Alumina,” J. Mater. Sci., 29, 1656–61 (1994). 8 F. F. Lange and K. C. Radford, “Healing of Surface Cracks in Polycrystalline Al2O3,” J. Am. Ceram. Soc., 53 [10–11] 420–21 (1970). 9 T. K. Gupta, “Crack Healing and Strengthening of Thermally Shocked Alumina,” J. Am. Ceram. Soc., 59 [5–6] 259–62 (1976). 10A. M. Thompson, H. M. Chan, M. P. Harmer, and R. F. Cook, “Crack Healing and Stress Relaxation in Al2O3–SiC ‘Nanocomposites’,” J. Am. Ceram. Soc., 78 [3] 567–71 (1995). 11. J. E. Moffatt, W. J. Plumbridge, and R. Hermann, “High Temperature Crack Annealing Effect on Fracture Toughness of Alumina and Alumina–SiC Composite,” Br. Ceram. Trans., 95 [1] 23–29 (1996). 12I. A. Chou, H. M. Chan, and M. P. Harmer, “Effect of Annealing Environment on the Crack Healing and Mechanical Behavior of Silicon Carbide-Reinforced Alumina Nanocomposites,” J. Am. Ceram. Soc., 81 [5] 1203–208 (1998). 13B. S. Kim, K. Ando, M. C. Chu, and S. Saito, “Crack-Healing Behavior of Monolithic Alumina and Strength of Crack-Healed Member” (in Jpn.), J. Soc. Mater. Sci. Jpn., 52, 667–73 (2003). 14J. J. Petrovic and L. A. Jacobson, “Controlled Surface Flaws in Hot-Pressed SiC,” J. Am. Ceram. Soc., 59 [1–2] 34–37 (1976). 15S. R. Choi and V. Tikare, “Crack Healing Behavior of Hot Pressed Silicon Nitride Due to Oxidation,” Scr. Metall. Mater., 26, 1263–68 (1992). 16M. C. Chu, S. Sato, Y. Kobayashi, and K. Ando, “Damage Healing and Strengthening Behaviour in Intelligent Mullite/SiC Ceramics,” Fatigue Fract. Eng. Mater. Struct., 18 [9] 1019–29 (1995). 17K. Ando, T. Ikeda, S. Sato, F. Yao, and Y. Kobayashi, “A Preliminary Study on Crack Healing Behaviour of Si3N4/SiC Composite Ceramics,” Fatigue Fract. Eng. Mater. Struct., 21 [1] 119–22 (1998). 18Y. H. Zhang, L. Edwards, and W. J. Plumbridge, “Crack Healing in a Silicon Nitride Ceramics,” J. Am. Ceram. Soc., 81 [7] 34–37 (1998). 19K. Ando, M. C. Chu, S. Sato, F. Yao, and Y. Kobayashi, “The Study on Crack Healing Behavior of Silicon Nitride Ceramics” (in Jpn.), Jpn. Soc. Mech. Eng., 64 [623] 1936–42 (1998). 20K. Ando, M. C. Chu, F. Yao, and S. Sato, “Fatigue Strength of Crack Healed Si3N4/SiC Composite Ceramics,” Fatigue Fract. Eng. Mater. Struct., 22 [10] 897–903 (1999). 21K. Ando, M. C. Chu, Y. Kobayashi, F. Yao, and S. Sato, “Crack Healing Behavior and High Temperature Strength of Silicon Nitride Ceramics” (in Jpn.), Jpn. Soc. Mech. Eng., 65 [633] 1132–39 (1999). 22K. Ando, K. Tsuji, T. Hirasawa, Y. Kobayashi, M. C. Chu, and S. Sato, “Crack Healing Behavior and High Temperature Strength of Mullite/SiC Composite Ceramics” (in Jpn.), J. Soc. Mater. Sci. Jpn., 48 [5] 484–94 (1999). 23Y. Korous, M. C. Chu, M. Nakatani, and K. Ando, “Crack Healing Behavior of SiC Ceramics,” J. Am. Ceram. Soc., 83 [11] 2788–92 (2000). 24F. Yao, K. Ando, M. C. Chu, and S. Sato, “Crack-Healing Behavior, HighTemperature and Fatigue Strength of SiC-Reinforced Silicon Nitride Composite,” J. Mater. Sci. Lett., 19 [12] 1081–83 (2000). 25K. Ando, K. Tsuji, M. Ariga, and S. Sato, “Fatigue Strength Properties of Crack Healed Mullite/SiC Composite Ceramics” (in Jpn.), J. Soc. Mater. Sci. Jpn., 48 [10] 1173–78 (1999). 26F. Yao, K. Ando, M. C. Chu, and S. Sato, “Static and Cyclic Fatigue Behaviour of Crack-Healed Si3N4/SiC Composite Ceramics,” J. Eur. Ceram. Soc., 21, 991–97 (2001). 27K. Ando, K. Furusawa, M. C. Chu, T. Hanagata, K. Tuji, and S. Sato, “Crack-Healing Behavior under Stress of Mullite/Silicon Carbide Ceramics and the Resultant Fatigue Strength,” J. Am. Ceram. Soc., 84 [9] 2073–78 (2001). 28K. Ando, M. C. Chu, K. Tsuji, T. Hirasawa, Y. Kobayashi, and S. Sato, “Crack Healing Behavior of Mullite/SiC Composite Ceramics,” J. Eur. Ceram. Soc., 22, 1313–19 (2002). 29K. Ando, K. Houjyou, M. C. Chu, S. Takeshita, K. Takahashi, S. Sakamoto, and S. Sato, “Crack-Healing Behavior of Si3N4/SiC Ceramics under Stress and Fatigue Strength at the Temperature of Healing (1000°C),” J. Eur. Ceram. Soc., 22, 1339–46 (2002). 30K. Ando, K. Takahashi, S. Nakayama, and S. Saito, “Crack-Healing Behavior of Si3N4/SiC Ceramics under Cyclic Stress and Resultant Fatigue Strength at the Healing Temperature,” J. Am. Ceram. Soc., 85 [9] 2268–72 (2002). Fig. 4. Effect of test temperature on the bending strength of a crackhealed specimen for Al2O3/SiC-W and monolithic Al2O3. 13 The data marked with an asterisk indicate the fracture occurred outside of the crack-healed zone. 2146 Journal of the American Ceramic Society—Takahashi et al. Vol. 86, No. 12