Mechanical Properties of Melt-Grown Alumina-Yttrium Aluminum Garnet Eutectics up to 1900 K

• Published in: Journal of the American Ceramic Society Vol. 88; no. 6; pp. 1488 - 1495
• Main Authors: Pastor, José Y., LLorca, Javier, Salazar, Alicia, Oliete, Patricia B., De Francisco, Isabel, Peña, José I.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Inc 01.06.2005; Blackwell; Wiley Subscription Services, Inc
• Subjects: Aluminum composites; Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Cermets, ceramic and refractory composites; Chemical industry and chemicals; Cross-disciplinary physics: materials science; rheology; Eutectics; Exact sciences and technology; High temperature; Materials science; Mechanical properties; Microstructure; Other materials; Physics; Specific materials; Structural ceramics; Technical ceramics; Ceramic matrix composite; Scanning electron microscopy; Laser heating; Aluminium Yttrium Oxides Mixed; Temperature effect; Mechanical properties; High temperature; Floating zone; Experimental study; Oxide ceramics; Composite material; Structural ceramic; Eutectic; Sintering; Manufacturing; Garnet type compound; Alumina
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1551-2916.2005.00265.x

Alumina/yttrium aluminum garnet (YAG) eutectic rods of 1 mm in diameter were grown by the laser‐heated floating zone method at different rates to obtain microstructures with the same morphology but of very different domain size. The mechanical properties of the rods (hardness, toughness, strength) were measured at ambient temperature in the longitudinal and transverse directions and, in addition, the longitudinal flexure strength was determined up to 1900 K. The fracture resistance and the hardness of the eutectics at ambient temperature were isotropic and independent of the domain size. On the contrary, the longitudinal strength was significantly higher than the transverse one and increased linearly with the growth rate, reaching almost 2 GPa in the rods grown at 750 mm/h, which presented a submicrometer homogeneous microstructure. The critical defect size was equivalent to that of Al2O3 and YAG domains in the microstructure, and the strength was proportional to the inverse of the square root of the domain size. In addition, the strength retention of the eutectics was remarkable, and the rods with the finest microstructure withstood 1.53 GPa at 1900 K. The moderate reduction in strength at very high temperature was induced by the homogeneous coarsening of the microstructure.