Fracture toughness and microstructure characteristic for in-situ Al2O3/YAG/ZrO2 eutectic composite by laser remelting

Fabrication of ceramic eutectic composites grown from melt is an advanced method with high efficiency. Improved properties are obtained in contrast to the conventional multi-step fabrication methods of fiber reinforced/sintered composites for high temperature use. In this study, Al2O3/YAG/ZrO2 ternary eutectic rods (phi 6x25mm(3)) are unconfined and fabricated from melt by directional solidification using laser remelting technique. The rapid solidification microstructure characteristic and fracture toughness are investigated. In comparison with the sintered composite of the same composition, laser remelted eutectics of Al2O3/YAG/ZrO2 have a different microstructure showing an ultra-fine interpenetrating network structure of interlamellar spacing less than 0.3 mu m, which decreases with increasing the laser scanning rate. Free of grain boundaries and interlocked phases in the submicron range are observed and of the basis for the improvement of mechanical properties. The mean values obtained in Al2O3/YAG/ZrO2 eutectic rods are H nu=16.7Gpa and K-k = 8.0MPam(1/2), respectively. and the toughening mechanism are briefly discussed.