Microstructure and Mechanical Properties of Al₂O₃/ZrO₂ Directionally Solidified Eutectic Ceramic Prepared by Laser 3D Printing

Directionally solidified eutectic ceramics such as Al₂O₃/ZrO₂ are promising structural materials for applications in harsh environment with an ultrahigh temperature. In this work, through adopting assistant heating laser 3D printing, Al₂O₃/ZrO₂ eutectic samples were manufactured with suppressing the formation of cracks. The dependence of the average rod spacing (λ_av) on the scanning rate (V) follows a relation with λ_avV^0.5 = 1 μm^1.5 s^-0.5. Typical eutectic microstructures, so-called complex regular, were analyzed with respect to its evolution with modulating the growth conditions. Formation mechanism of the solidification defect, shrinkage porosity, was discussed and the defect is found to be significantly suppressed by optimizing the solidification parameters. The maximum hardness and fracture toughness are measured to be 16.7 GPa and 4.5 MPa m^1/2, respectively. The interplay between the propagation of cracks and the Al₂O₃/ZrO₂ interface is discussed.