S Ji et al. /Journal of the European Ceramic Society 25 (2005)301-311 CAS s 2 mm 0.1mm Fig. 10. Optical microstructures of deformed samples. Crossed polarizers with an auxiliary gypsum plate. The different colors reflect different crystallographic orientations. (a)A CAS layer from a layered composite(sample J22) shortened axially at 300 MPa, 1373K, I and 32% strain(b)A particulate composite(sample J14)containing 50 vol. quartz(coarse clasts)and 50 vol. CAS (fine grains), shortened axially at 300 MPa, 1273K, 10-s-I and 31% strain. The foliation(S) is perpendicular to the compression direction (o1). The blue CAS grains align their(0 10)and [100 nearly parallel to the foliation. The PC samples are characterized by a plastically flowing 1120 and [112 1 Hence the observed shape preferred CAS matrix containing almost rigid Qtz clasts(Fig. 10b). orientation of Qtz(Fig. 10b) is most likely due to rigid ro- The Cas laths and polycrystalline fibers developed a marked tations of elongate grains in the axially compressive strain foliation that is deflected around large Qtz clasts in which field. In contrast, the CAS matrix developed a strong CPO undulatory extinction is the sole feature of incipient plastic as indicated by the optically parallel extinction or uniform deformation. Measurements show that Qtz has almost same color in cross polarized light with an auxiliary gypsum plate average grain size and aspect ratio in deformed(Fig. 12)(Fig. 10b), which can be also interpreted as the result of and undeformed(Fig. 3)particulate composites, confirm- dislocation slip on the(0 10)[100] system. Our optical ob- ing that Qtz grains have not deformed plastically. EBSD servations qualitatively suggest that CAs in the particulate measurements of Qtz grains from a PC aggregate(sample composites containing 50 vol. Qtz develops the same pat- J14)shortened 31% at 1273 K and a constant strain rate of tern and strength of CPO as that in pure CAs aggregates, if 10-s show no preferred orientation of poles to (1010) we compare samples which deformed at the same conditionsS. Ji et al. / Journal of the European Ceramic Society 25 (2005) 301–311 307 Fig. 10. Optical microstructures of deformed samples. Crossed polarizers with an auxiliary gypsum plate. The different colors reflect different crystallographic orientations. (a) A CAS layer from a layered composite (sample J22) shortened axially at 300 MPa, 1373 K, 10−5 s−1 and 32% strain. (b) A particulate composite (sample J14) containing 50 vol.% quartz (coarse clasts) and 50 vol.% CAS (fine grains), shortened axially at 300 MPa, 1273 K, 10−5 s−1 and 31% strain. The foliation (S) is perpendicular to the compression direction (σ1). The blue CAS grains align their (0 1 0) and [1 0 0] nearly parallel to the foliation. The PC samples are characterized by a plastically flowing CAS matrix containing almost rigid Qtz clasts (Fig. 10b). The CAS laths and polycrystalline fibers developed a marked foliation that is deflected around large Qtz clasts in which undulatory extinction is the sole feature of incipient plastic deformation. Measurements show that Qtz has almost same average grain size and aspect ratio in deformed (Fig. 12) and undeformed (Fig. 3) particulate composites, confirm￾ing that Qtz grains have not deformed plastically. EBSD measurements of Qtz grains from a PC aggregate (sample J14) shortened 31% at 1273 K and a constant strain rate of 10−5 s−1 show no preferred orientation of poles to {1 0 1 0¯ }, {1 1 2 0¯ } and {1 1 2 1¯ }. Hence the observed shape preferred orientation of Qtz (Fig. 10b) is most likely due to rigid ro￾tations of elongate grains in the axially compressive strain field. In contrast, the CAS matrix developed a strong CPO as indicated by the optically parallel extinction or uniform color in cross polarized light with an auxiliary gypsum plate (Fig. 10b), which can be also interpreted as the result of dislocation slip on the (0 1 0)[1 0 0] system. Our optical ob￾servations qualitatively suggest that CAS in the particulate composites containing 50 vol.% Qtz develops the same pat￾tern and strength of CPO as that in pure CAS aggregates, if we compare samples which deformed at the same conditions