D.-K. Kim, W.M. Kriven/ Composites: Part B 37(2006)509-514 Table 4 delamination after sintering. The thermal expansion coeffi The strength and work of fracture of oxide laminated composites cients of3Y- TZP and alpo4are10.2and2.3×10-°°C, Work of respectively, [57]. The reason for delamination of the MPa) fracture composite is attributed to the large thermal expansion ( k/m) coefficient mismatch. Fig. 5 shows the load vs displacement 157±16 0.46+0.03 curve from bend testing of the 50 vol% alumina 50 vol% YAG Al2O3(600 um)-AlPO4(75 um) 161±15 50 vol% Al,O3. 50 vol% YAG in situ 181±10 0. 26+0.06 in situ composite matrix-alumina platelet interphase, indicating omposite(600 um)-AIPO4(75 um) quasi-elastic'load vs displacement behavior. The composite 50 vol% Al,O3. 50 vol% YAG in situ 188±8 065±0.02 underwent almost 0.35 mm of displacement. The SEM composite(600 um)-alumina platelets micrograph of the 3-point, bend-tested, 50 vol% alumina. 50 (75m) vol% YAG in situ composite matrix-alumina platelet 3Y-TZP(600 um)-AIPO4(75 um) Delamination laminated composite is shown in Fig. 6. The crack was deflected along the alumina platelet interphase layer and 4. Conclusions Various oxide-oxide laminated composites were fabricated having porous AlPO4 or alumina platelets as crack deflecting terphases. Tape casting formulations for oxide materials with powder loadings of 25.1 vol%, were developed. In the case of loading of 30 vol%o was used. The AlPO. was chemically compatible with alumina, mullite and zirconia during various high-temperature annealing conditions between 1550 and 1600C. However, AlPOa 00.050.10.15020250.30.35 reacted with YAg in the 50 vol%o alumina 50 vol% YAG in situ composite matrix, forming YPO4. The 50 vol%o alumina- 50 vol% YAG in situ composite matrix itself had an Fig. 5. The load vs displacement curve for the 3-point bending test of 50 vol% average 361+19 MPa 3-point bending strength, in which the ol% YAG in situ matrix-AlPOa laminated composite. grain sizes of the alumina and YAG were 2.1 and 2. 4 um, reaction of the AlPO4 to form YPOa at the interface, so that the respectively, after sintering at 1700C for 5 h. Alumina- AlPO4 could no longer function as a weak, porous, crack. AlPO4, mullite-AlPO4, 50 vol% alumina 50 vol% YAG in situ composite matrix-alumina platelet laminated composites deflecting interphase. The 50 vol% alumina. 50 vol% YAG showed some graceful failure and had works of fracture of exhibited non-brittle fracture, and had a strength and a work of 0.46+0.03, 0.47+0.05, and 0.65+0.02 kJ/m, respectively The 50 vol%o alumina. 50 vol%YAG in situ composite matrix fracture of 188+8 MPa and 0.65+0.02 kJ/m, respectively. AlPO4 laminated composite showed brittle fracture because of The 3Y-TZP-AlPO4 laminated composite showed reaction of AlPO, to form YPO 4 within the interphase. The 3Y TZP-AlPOA laminated composite was delaminated because of too large a mismatch in the thermal expansion coefficients. References 50% ALOs in situ composite [1] Boch P, Chartier T, Huttepain M. J Am Ceram Soc 1986: 69: C191 [2 Plucknett KP, Caceres CH, Hughes C, Willinson DS. J Am Ceram Soc 1994;77:214 [3] Requena J, Moreno R, Moya JS. J Am Ceram Soc 1989: 72: 1511 [4] Takebe H, Morgana K. Yogoyo Kyokaishi 1988: 96: 1149 [5] Sarkar P, Haung X, Nicholson PS. J Am Ceram Soc 1992: 75: 290 [6] Whitehead M, Sarkar P, Nicholson PS. Ceram Eng Sci Proc 1994: 15 1110. [7 Wang H, Hu X J Am Ceram Soc 1996: 79: 553 18 Marshall DB, Ratto JJ. J Am Ceram Soc 1991: 74: 2979 [91 Morgan PED, Marshall DB. J Am Ceram Soc 1995: 78: 1553 Fig. 6. Crack deflection along alumina platelet interphases in the laminate 1 Clegg WJ. Acta Metall Mater 1992: 40: 3085 composed of 50 vol% Al2O3. 50 vol% YAG in situ composite matrix and [12] Shannon T, Blackburn S Ceram Eng Sci Proc 1995: 16: 1115. alumina platelets(corresponding to the specimen in Fig. 5). [13 Chartier T, Merle D, Besson JL. J Eur Ceram Soc 1995; 15: 101reaction of the AlPO4 to form YPO4 at the interface, so that the AlPO4 could no longer function as a weak, porous, crack￾deflecting interphase. The 50 vol% alumina$50 vol% YAG in situ composite matrix-alumina platelet laminated composite exhibited non-brittle fracture, and had a strength and a work of fracture of 188G8 MPa and 0.65G0.02 kJ/m2 , respectively. The 3Y-TZP–AlPO4 laminated composite showed delamination after sintering. The thermal expansion coeffi- cients of 3Y-TZP and AlPO4 are 10.2 and 2.3!10K6 /8C, respectively, [57]. The reason for delamination of the composite is attributed to the large thermal expansion coefficient mismatch. Fig. 5 shows the load vs displacement curve from bend testing of the 50 vol% alumina$50 vol% YAG in situ composite matrix-alumina platelet interphase, indicating ‘quasi-elastic’ load vs displacement behavior. The composite underwent almost 0.35 mm of displacement. The SEM micrograph of the 3-point, bend-tested, 50 vol% alumina$50 - vol% YAG in situ composite matrix-alumina platelet, laminated composite is shown in Fig. 6. The crack was deflected along the alumina platelet interphase layer and showed a complicated crack path. 4. Conclusions Various oxide–oxide laminated composites were fabricated having porous AlPO4 or alumina platelets as crack deflecting interphases. Tape casting formulations for oxide materials with powder loadings of 25.1 vol%, were developed. In the case of tape casting of alumina platelets, a solid loading of 30 vol% was used. The AlPO4 was chemically compatible with alumina, mullite and zirconia during various high-temperature annealing conditions between 1550 and 1600 8C. However, AlPO4 reacted with YAG in the 50 vol% alumina$50 vol% YAG in situ composite matrix, forming YPO4. The 50 vol% alumina$50 vol% YAG in situ composite matrix itself had an average 361G19 MPa 3-point bending strength, in which the grain sizes of the alumina and YAG were 2.1 and 2.4 mm, respectively, after sintering at 1700 8C for 5 h. Alumina– AlPO4, mullite-AlPO4, 50 vol% alumina$50 vol% YAG in situ composite matrix-alumina platelet laminated composites showed some graceful failure and had works of fracture of 0.46G0.03, 0.47G0.05, and 0.65G0.02 kJ/m2 , respectively. The 50 vol% alumina$50 vol% YAG in situ composite matrix￾AlPO4 laminated composite showed brittle fracture because of reaction of AlPO4 to form YPO4 within the interphase. The 3Y￾TZP–AlPO4 laminated composite was delaminated because of too large a mismatch in the thermal expansion coefficients. References [1] Boch P, Chartier T, Huttepain M. J Am Ceram Soc 1986;69:C191. [2] Plucknett KP, Caceres CH, Hughes C, Willinson DS. J Am Ceram Soc 1994;77:2145. [3] Requena J, Moreno R, Moya JS. J Am Ceram Soc 1989;72:1511. [4] Takebe H, Morigana K. Yogoyo Kyokaishi 1988;96:1149. [5] Sarkar P, Haung X, Nicholson PS. J Am Ceram Soc 1992;75:2907. [6] Whitehead M, Sarkar P, Nicholson PS. Ceram Eng Sci Proc 1994;15: 1110. [7] Wang H, Hu X. J Am Ceram Soc 1996;79:553. [8] Marshall DB, Ratto JJ. J Am Ceram Soc 1991;74:2979. [9] Morgan PED, Marshall DB. J Am Ceram Soc 1995;78:1553. [10] Clegg WJ, Kendall K, Alford NM, Button TW, Birchall JD. Nature 1990; 347:455. [11] Clegg WJ. Acta Metall Mater 1992;40:3085. [12] Shannon T, Blackburn S. Ceram Eng Sci Proc 1995;16:1115. [13] Chartier T, Merle D, Besson JL. J Eur Ceram Soc 1995;15:101. Table 4 The strength and work of fracture of oxide laminated composites Strengh (MPa) Work of fracture (kJ/m2 ) Mullite (600 mm)–AlPO4 (75 mm) 157G16 0.46G0.03 Al2O3 (600 mm)–AlPO4 (75 mm) 161G15 0.47G0.05 50 vol% Al2O3$50 vol% YAG in situ composite (600 mm)–AlPO4 (75 mm) 181G10 0.26G0.06 50 vol% Al2O3$50 vol% YAG in situ composite (600 mm)–alumina platelets (75 mm) 188G8 0.65G0.02 3Y-TZP (600 mm)–AlPO4 (75 mm) Delamination Fig. 5. The load vs displacement curve for the 3-point bending test of 50 vol% Al2O3$50 vol% YAG in situ matrix-AlPO4 laminated composite. Fig. 6. Crack deflection along alumina platelet interphases in the laminate composed of 50 vol% Al2O3$50 vol% YAG in situ composite matrix and alumina platelets (corresponding to the specimen in Fig. 5). D.-K. Kim, W.M. Kriven / Composites: Part B 37 (2006) 509–514 513