Microstructure and fracture toughness of directionally solidified Al₂O₃/Y₃ Al₅O₁₂(YAG) eutectic by laser zone melting

Al₂O₃/Y₃ Al₅O₁₂(YAG) eutectic ceramic was prepared from melt by laser-zone-melting with directional solidification technique to study the relationship between the eutectic microstructure and the processing parameters, and its mechanical property was investigated as well. The analysis results show that the scanning rate and power density strongly affect the eutectic microstructure. With the processing parameters adjusted properly, the binary Al₂O₃/YAG has a uniform and homogeneous lamella microstructure, in which single-crystal Al₂O₃and single-crystal YAG are three-dimensionally and continuously reticularly connected and finely coupled without grain boundaries, colonies and amorphous phases between interfaces. Eutectic spacing is only around 1-2 μm and is diminished with the scanning rate' s increasing. The maximum hardness reaches 19.5 GPa and the fracture toughness at room temperature is attained for 3.6 MPa·m^1/2 by Vickers indentation method.