A R. de Arellano-Lopez et al /Internatonal Jownal of Refractory Metals Hard Matenals 16(1998)337-341 microcracking can play a role as the thermal expansion Microstructural features of both undeformed and mismatch between the three phases is significant. deformed specimens were examined using X-ray ee-and four-point bending strengths of AISiTi were diffraction, scanning electron microscopy (SEM), and 825 and 680 MPa, respectively. Tensile surfaces were, transmission electron microscopy (TEM). SEM however,not polished. High-temperature compressive samples were prepared by polishing the composite to a creep of this composite has been investigated at 1 um finish and coating with carbon. TEM foils were 1350-1450oC in inert atmospheres [11]. The creep prepared by grinding, dimpling and ion-milling resistance is good and, at lower stresses, deformation Preparation of TEM foils was complicated because the occurs by partially unaccommodated grain-boundary iC particles proved to be very difficult to thin by ion-milling. Information about the micromorphology of High-temperature mechanical properties play an the phases has been published previously [11]:alt important role in development and implementation of actical applications of ceramic composites because many of the potential applications are at elevated temperatures. Therefore this work is aimed at measuring the high-temperature fracture strength and CIO\ creep response of an AISiTi composite. Additionally, the elastic modulus was measured to 1000C 2. Experiments A commercial composite(CRYSTALOY 231IEDX fabricated by hot-pressing at 1700-1800'C a mixture of 30.9 vol. SiC whiskers, 23.0 vol. TiC powder and balance AlO, was examined 7]. Optical micrographs of the Sic whiskers and a surface polished perpen dicular to the hot-pressing direction are shown in Fig 1. The material is x% dense. Comparison of the O) pun initial(Fig. 1(a))and final whisker lengths(Fig. 1(b)) indicated that considerable damage to the Sic whisker occurred during processing. X-ray diffraction showed strong TiC and Al2O3 peaks and weaker SiC peak Bend-bar samples25×3.8×38mmor2.5×3.0×38 mm were cut with a slow-speed diamond saw. Bar dges were chamfered and each tensile surface was polished with 1 uam diamond paste. Bending strength tests were performed at a crosshead velocity of a1.3 mm/min in an Instron Model 1125 [12]. Room temperature tests were conducted in air with steel tooling, inner load span of 9.5 mm, outer load span of 23.8 mm. High-temperature tests were conducted in Ar with AlO3-SiC whisker tooling [5], inner load span of 9.9 mm, outer load span 17.6 mm. The elastic modulus was measured by a resonance frequency method [13] For creep, parallelepipeds≈5×2×2 mm were cut and the compression surfaces were polished to be flat and parallel. Specimen do m 1350-1450C under uniaxial compression in the direc- tion of the longer axis. The low-stress range was studied in Ar with a constant-load (CL)cree apparatus [14; higher stresses and strain rates were omposIte, where the bright grains are TiC particles, the light-grey studied in high-purity N2 at approximately constant filaments are the SiC whiskers, and the dark-grey background is the strain rate(CSR)[12 alumina matrix338 A R. de AlelIano-L6pez et al /International Jownal of Refractory Metals & Hard Matertals 16 (1998) 337-341 microcracking can play a role as the thermal expansion mismatch between the three phases is significant. Three- and four-point bending strengths of A1SiTi were 825 and 680 MPa, respectively. Tensile surfaces were, however, not polished. High-temperature compressive creep of this composite has been investigated at 1350-1450°C in inert atmospheres [11]. The creep resistance is good and, at lower stresses, deformation occurs by partially unaccommodated grain-boundary sliding. High-temperature mechanical properties play an important role in development and implementation of practical applications of ceramic composites because many of the potential applications are at elevated temperatures. Therefore, this work is aimed at measuring the high-temperature fracture strength and creep response of an A1SiTi composite. Additionally, the elastic modulus was measured to 1000°C. 2. Experiments A commercial composite (CRYSTALOY 2311EDX) fabricated by hot-pressing at 1700-1800°C a mixture of 30.9 vol.% SiC whiskers, 23.0 vol.% TiC powder and balance A1,O3 was examined [7]. Optical micrographs of the SiC whiskers and a surface polished perpen￾dicular to the hot-pressing direction are shown in Fig. 1. The material is ~99% dense. Comparison of the initial (Fig. l(a)) and final whisker lengths (Fig. l(b)) indicated that considerable damage to the SiC whisker occurred during processing. X-ray diffraction showed strong TiC and A1203 peaks and weaker SiC peaks. Bend-bar samples 2.5 x 3.8 x 38 mm or 2.5 x 3.0 x 38 mm were cut with a slow-speed diamond saw. Bar edges were chamfered and each tensile surface was polished with 1 #m diamond paste. Bending strength tests were performed at a crosshead velocity of ~ 1.3 ram/rain in an Instron Model 1125 [12]. Room￾temperature tests were conducted in air with steel tooling, inner load span of 9.5 ram, outer load span of 23.8 ram. High-temperature tests were conducted in Ar with A1203-SiC whisker tooling [5], inner load span of 9.9 mm, outer load span 17.6 mm. The elastic modulus was measured by a resonance frequency method [13]. For creep, parallelepipeds ~5 x 2 x 2 mm were cut and the compression surfaces were polished to be flat and parallel. Specimens were deformed at 1350-1450°C under uniaxial compression in the &rec￾tion of the longer axis. The low-stress range was studied in Ar with a constant-load (CL) creep apparatus [14]; higher stresses and strain rates were studied in high-purity N2 at approximately constant strain rate (CSR) [12]. Microstructural features of both undeformed and deformed specimens were examined using X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SEM samples were prepared by polishing the composite to a 1 ltm finish and coating with carbon. TEM foils were prepared by grinding, dimpling and ion-milling. Preparation of TEM foils was complicated because the TiC particles proved to be very difficult to thin by ion-milling. Information about the micromorphology of the phases has been published previously [11]: alumina Fig. 1 Optical photomicrographs of (a) SIC whiskers and (b) A1SIT~ composite, where the bright grams are TIC parUcles, the hght-grey filaments are the SiC whiskers, and the dark-grey background is the alumina matrLx