Microstructure and Fracture Toughness of Al_2O_3/Er_3Al_5O_(12) Eutectic Ceramic Prepared by Laser Zone Remelting

Directionally solidified Al2O3/Er3Al5O12(EAG) eutectic ceramic was prepared by laser zone remelting technique.The eutectic morphology and microstructure evolution investigated as a function of laser scanning rate.Moreover,the mechanical properties and toughening mechanisms were studied.The Al2O3/EAG eutectic ceramic consists of only two continuous phases of Al2O3 and EAG which interpenetrates with each other to form well-distributed three-dimensional network.The eutectic spacing is only around 0.2-2.1μm and reduces with the increase of scanning rate.At low scanning rate,the typical lamellar irregular eutectic structure is obtained.When the scanning rate reaches 800μm/s,the cellular or dendrite microstructure appears.The hardness and the fracture toughness at room temperature are measured to be 18.7GPa and 2.45MPa.m1/2,respectively.The refined micro-structure,crack deflection at phase interface and crack branching contribute to the improved toughness.