Microstructure and fracture toughness of Al₂O₃/ Er₃Al₅O₁₂ 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 0.2-2.1 μm 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 800 μm/s, the cellular or dendrite microstructure appears. The hardness and the fracture toughness at room temperature are measured to be 18.7 GPa and 2.45 MPa·m^1/2, respectively. The refined microstructure, crack deflection at phase interface and crack branching contribute to the improved toughness.