Fabrication of Al<sub>2</sub>O<sub>3</sub>/YAG eutectic ceramics utilizing a fast combustion reaction heating method

Abstract

Al2O3/Y3Al5O12(YAG) eutectic ceramics are considered to be candidate materials for use in high temperature and oxidizing environments owing to their remarkable thermodynamic stabilities. Many techniques have been used to prepare eutectic ceramics, including the Bridgeman, edge-defined film-fed growth, micro-pulling-down, floating zone, and laser zone re-melting methods. However, these methods use complex high temperature equipment. In this work, simple equipment was used to achieve combustion reaction heating with the advantages of a high heating rate (2000℃/min), high temperature, and high cooling rate. Using this set-up we could melt and fabricate eutectic ceramics. The microstructure and physical properties of the obtained Al2O3/YAG eutectic ceramics were studied. The eutectic ceramics consisted of Al2O3 and YAG phases. The two phases exhibited coupled growth with well-matched and clean phase boundaries. Several special morphologies were obtained besides the typical Chinese script microstructure, and their formation mechanisms are discussed. The Vickers hardness of the eutectic ceramics was 20.52 GPa, which is higher than that previously reported for any binary eutectic ceramic system. The fracture toughness was 2.64 MPa m1/2, which is slightly higher than about 2 MPa m1/2 previously reported. The crack propagated in a straight line from the indentation corner and did not deflect at the interface between the Al2O3 and YAG domains, compared with the intergranular fracture in the hot-pressed sample. This weak interaction of the crack path with the microstructure was induced by the absence of residual stress and the excellent bonding between the eutectic phases. Samples treated at 1500℃ for 20 h exhibited no weight loss or obvious change in microstructure, indicating the high temperature stability of these eutectic ceramics.