D-K. Kim, W.M. Kriven/Materials Science and Engineering 4 380 (2004)237-244 500 microns 25 500 microns M少 Fig 9. SEM micrographs of the sintered mullite-AlPO4, two-layer, fibrous monolithic composite (M: matrix center rod (mullite), 1: porous interpha Fig. 10. SEM micrographs of the sintered 50 vol. alumina: 50 vol.% layer(AlPO4)). mullite matrix and AlPO4 interphase formed a homogeneous and uniform microstructure Fig. 9(a and b)are SEM micrographs of the sintered mullite-AlPO4, two-layer, fibrous monolithic composite The two composites were mechanically evaluated by The microstructure is homogeneous, and the higher mag- 3-point bend testing and the load versus displacement nification image confirms that the AlPO4 interphase layer curves are given in Fig. 11. The two-layer, mullite-AlPO was porous. SEM micrograph of the sintered 50 vol. fibrous monolithic composite exhibited apparent non-brittle alumina: 50 vol. YAG in situ composite matrix-alumina fracture behavior with 0. 1 mm of displacement, and had platelet; fibrous monolithic composite are presented in a strength and work of fracture of 76+ 5 MPa and 0.45 Fig 10. The higher magnification micrograph of the inter- t 0.02 kJ/m, respectively. The graceful failure of the phase region, however, indicates that alumina platelets in mullite-AlPO4 composite, is attributed to crack deflection the layer had sintered together. Because of the high CIP- along the porous AlPO4 interphase as can be seen in Fig 12 ping pressure of 413. 7 MPa, the platelets in the interphase This SEM micrograph clearly shows that crack deflected region were thought to be compacted together without along the weak AlPO4 interphase On the other hand, the forming a porous pocket structure, which is necessary sintered 50 vol. alumina: 50 vol. YAG in situ composite for debonding to occur. Because the platelets were com- matrix-alumina platelet, two-layer fibrous monolithic com- pacted together after CIPping and the composite pellet was posite underwent brittle fracture, showing a displacement sintered at 1650C for 15h, the alumina platelets grains less than 0.02 mm, and had a room temperature, 3-point grew to about 2-3 times larger compared to their starting bend strength and work of fracture of 219 t 7 MPa and sizes 0. 25+ 0.03 kJ/m, respectively. The reason for the brittle242 D.-K. Kim, W.M. Kriven / Materials Science and Engineering A 380 (2004) 237–244 Fig. 9. SEM micrographs of the sintered mullite-AlPO4, two-layer, fibrous monolithic composite. (M: matrix center rod (mullite), I: porous interphase layer (AlPO4)). mullite matrix and AlPO4 interphase formed a homogeneous and uniform microstructure. Fig. 9(a and b) are SEM micrographs of the sintered mullite-AlPO4, two-layer, fibrous monolithic composite. The microstructure is homogeneous, and the higher mag￾nification image confirms that the AlPO4 interphase layer was porous. SEM micrograph of the sintered 50 vol.% alumina:50 vol.% YAG in situ composite matrix–alumina platelet; fibrous monolithic composite are presented in Fig. 10. The higher magnification micrograph of the inter￾phase region, however, indicates that alumina platelets in the layer had sintered together. Because of the high CIP￾ping pressure of 413.7 MPa, the platelets in the interphase region were thought to be compacted together without forming a porous pocket structure, which is necessary for debonding to occur. Because the platelets were com￾pacted together after CIPping and the composite pellet was sintered at 1650 ◦C for 15 h, the alumina platelets grains grew to about 2–3 times larger compared to their starting sizes. Fig. 10. SEM micrographs of the sintered 50 vol.% alumina:50 vol.% YAG in situ composite matrix–alumina platelet interphase, forming a two-layer fibrous monolithic composite. (M: matrix center rod (50 vol.% alumina:50 vol.% YAG in situ composite), I: interphase layer (alumina platelets)). The two composites were mechanically evaluated by 3-point bend testing and the load versus displacement curves are given in Fig. 11. The two-layer, mullite-AlPO4 fibrous monolithic composite exhibited apparent non-brittle fracture behavior with ∼0.1 mm of displacement, and had a strength and work of fracture of 76 ± 5 MPa and 0.45 ± 0.02 kJ/m2, respectively. The graceful failure of the mullite-AlPO4 composite, is attributed to crack deflection along the porous AlPO4 interphase as can be seen in Fig. 12. This SEM micrograph clearly shows that crack deflected along the weak AlPO4 interphase. On the other hand, the sintered 50 vol.% alumina:50 vol.% YAG in situ composite matrix–alumina platelet, two-layer fibrous monolithic com￾posite underwent brittle fracture, showing a displacement less than 0.02 mm, and had a room temperature, 3-point bend strength and work of fracture of 219 ± 7 MPa and 0.25 ± 0.03 kJ/m2, respectively. The reason for the brittle