D.-K. Kim, W.M. Kriven/Composites: Part B 37(2006)509-514 Mechanical prope Bending strength(MPa) Fracture toughness(MPa Creep properties C 25° 1000℃C AlO[471 380(100% 350092%) 280(74%) 3.3(100%) 2.5(76%) 24(73%) c-Axis sapphire: best creep Mullite [491 240(100% 240(100%) 250(104%)23(100%) 2.5(109%) 2.8(122%) Approximately an order rate than that of 02[5 Zro 1511 790(100% 200(25%) 7(100% 2(29%) YAG 52 230(100%) 210(91%) 200(87%) 1.5(100%)1.3(87%) 14093%) [110 and [1l1] YAG has higher creep resistance to c-axis sapphire [531 Alumina Yag 420(100% 4.3(100%) 4.1(95%) .9091%) The creep resistance is eutectic composi better than that of poly- 54,55 rystalline YAG and that The variations of the mechanical properties of the oxide deflecting phases, are summarized in Table 4. The Al2O3- matrix materials as a function of temperature were gathered AlPO4 laminated composite showed non-brittle fracture and from the literatures and the results are summarized in Table 2. had a bending strength and work of fracture of 161+ 15, and Alumina had a bending strength of 380 MPa at room 0.47+0.05 kJ/m, respectively. The 50 vol% alumina. 50 temperature, and held 74% of its room temperature strength vol% YAG in situ composite matrix-AlPOA laminated at 1300C. Mullite had a higher strength and work of fracture composite also showed brittle fracture and had a bend strength at 1300C than at room temperature. The mullite had 250 and and work of fracture of 181+10 MPa and 0.26+0.06 kJ/m 2. 8 MPa m values for bending strength and fracture respectively. The reason for this behavior is attributed to the toughness, respectively, at 1300C. The 3Y-TZP had the Table 3 The Al2O3 YAG eutectic composite had 420 and 4.3 MPa m2 ysical and mechanical properties of the four matrix materials used in this temperature, but the values decreased dramatically at 1000C of bending strength and fracture toughness, respectively, at Sintering 3-Point bend Average ondition (g/cm) grain slz room temperature. The composite retained 100 and 91% of its (um) room temperature bending strength and fracture toughness, Al-o 1600°/h3.40098%)437±13229 respectively, at 1300C [54,55]. The mullite, YAG,andMullite 600°C/10h3.13098% 308±11 Al2O3 YAG eutectic composites all possessed good reported 50 vol% Al2. 1700"C/5 h 61±19Al2O32.14, creep propertie 50 vol%c YAG:2.37 The oxide matrix materials were sintered at different composite temperatures, and their physical and mechanical properties 3Y-TZP 1550°/h6.03(99%)1073±46 0.52 were studied. Table 3 presents the results. The densities of the sintered Al,O3, mullite, and 3Y-TZP were 98, 98, and 99%o of theoretical density, respectively. The 3-point bending strengths of the alumina. mullite. 50 vol%o alumina. 50 vol% YAg in situ omposite matrix, and 3Y-TZP were 437+13, 308+11. 361+19, and 1073+46 MPa, respectively. The average grain sizes after sintering of Al,O3, mullite, and 3Y-TZP ere 2.3, 1.4 and 0.5 um, respectively. In the case of the 60 vol%o alumina 50 vol%o mullite in situ composite matrix, the average grain sizes of the alumina and YAG phases were 2.1 nd 2.4 um, respectively. A SEM micrograph of the Al2O3-AlPO4 laminated composite is shown in Fig. 4. The alumina layer was dense, the aluminum phosphate layer was porous, and interphase between the two materials indicated no delamination. The results of the 3-point bending tests for the laminated composites with mullite, alumina, zirconia, and 50 vol% alumina.50 vol% YAG in situ composite as matrix materials Fig 4. The SEM micrograph plateletsThe variations of the mechanical properties of the oxide matrix materials as a function of temperature were gathered from the literatures and the results are summarized in Table 2. Alumina had a bending strength of 380 MPa at room temperature, and held 74% of its room temperature strength at 1300 8C. Mullite had a higher strength and work of fracture at 1300 8C than at room temperature. The mullite had 250 and 2.8 MPa m1/2 values for bending strength and fracture toughness, respectively, at 1300 8C. The 3Y-TZP had the highest bending strength and fracture toughness at room temperature, but the values decreased dramatically at 1000 8C. The Al2O3$YAG eutectic composite had 420 and 4.3 MPa m1/2 of bending strength and fracture toughness, respectively, at room temperature. The composite retained 100 and 91% of its room temperature bending strength and fracture toughness, respectively, at 1300 8C [54,55]. The mullite, YAG, and Al2O3$YAG eutectic composites all possessed good reported creep properties. The oxide matrix materials were sintered at different temperatures, and their physical and mechanical properties were studied. Table 3 presents the results. The densities of the sintered Al2O3, mullite, and 3Y-TZP were 98, 98, and 99% of theoretical density, respectively. The 3-point bending strengths of the alumina, mullite, 50 vol% alumina$50 vol% YAG in situ composite matrix, and 3Y-TZP were 437G13, 308G11, 361G19, and 1073G46 MPa, respectively. The average grain sizes after sintering of Al2O3, mullite, and 3Y-TZP were 2.3, 1.4 and 0.5 mm, respectively. In the case of the 50 vol% alumina$50 vol% mullite in situ composite matrix, the average grain sizes of the alumina and YAG phases were 2.1 and 2.4 mm, respectively. A SEM micrograph of the Al2O3–AlPO4 laminated composite is shown in Fig. 4. The alumina layer was dense, the aluminum phosphate layer was porous, and interphase between the two materials indicated no delamination. The results of the 3-point bending tests for the laminated composites with mullite, alumina, zirconia, and 50 vol% alumina$50 vol% YAG in situ composite as matrix materials and aluminum phosphate and alumina platelets as crack deflecting phases, are summarized in Table 4. The Al2O3– AlPO4 laminated composite showed non-brittle fracture and had a bending strength and work of fracture of 161G15, and 0.47G0.05 kJ/m2 , respectively. The 50 vol% alumina$50 - vol% YAG in situ composite matrix-AlPO4 laminated composite also showed brittle fracture and had a bend strength and work of fracture of 181G10 MPa and 0.26G0.06 kJ/m2 , respectively. The reason for this behavior is attributed to the Table 2 Mechanical properties of six oxide ceramics Bending strength (MPa) Fracture toughness (MPa$m1/2) Creep properties 25 8C 1000 8C 1300 8C 25 8C 1000 8C 1300 8C Al2O3 [47] 380 (100%) 350 (92%) 280 (74%) 3.3 (100%) 2.5 (76%) 2.4 (73%) c-Axis sapphire: best creep resistant [48] Mullite [49] 240 (100%) 240 (100%) 250 (104%) 2.3 (100%) 2.5 (109%) 2.8 (122%) Approximately an order less creep rate than that of Al2O3 [50] ZrO2 [51] 790 (100%) 200 (25%) – 7 (100%) 2 (29%) 2 (29%) – YAG [52] 230 (100%) 210 (91%) 200 (87%) 1.5 (100%) 1.3 (87%) 1.4 (93%) [110] and [111] YAG has higher creep resistance to c-axis sapphire [53] Alumina YAG eutectic composite [54,55] 420 (100%) 420 (100%) 420 (100%) 4.3 (100%) 4.1 (95%) 3.9 (91%) The creep resistance is better than that of poly￾crystalline YAG and that of a-axis sapphire [56] Fig. 4. The SEM micrograph of the as-fabricated Al2O3–AlPO4 laminated composite. Table 3 The physical and mechanical properties of the four matrix materials used in this study Sintering condition Density (g/cm3 ) 3-Point bend strength (MPa) Average grain size (mm) Al2O3 1600 8C/3 h 3.40 (98%) 437G13 2.29 Mullite 1600 8C/10 h 3.13 (98%) 308G11 1.44 50 vol% Al2- O3$50 vol% YAG in situ composite 1700 8C/5 h – 361G19 Al2O3:2.14, YAG:2.37 3Y-TZP 1550 8C/1 h 6.03 (99%) 1073G46 0.52 512 D.-K. Kim, W.M. Kriven / Composites: Part B 37 (2006) 509–514