Growth characteristic and fracture toughness of laser rapidly solidified Al2O3/YAG/ZrO2 ceramic eutectic in situ composite

Directionally solidified oxide ceramic eutectic composites with superior strength, oxidation resistance, creep resistance, structural stability and low sensitivity to crack at high temperature have aroused much attention in recent years, and various preparation techniques have been developed. In situ fabrication of ceramic eutectic composites by laser rapid solidification is a cheap and quick method compared to conventional multi-step fabrication methods of fiber reinforced composites for high temperature use. In this paper, Al ₂O₃/YAG/ZrO₂ ternary eutectics are rapidly prepared from melt by directional solidification using laser zone remelting technique, the growth characteristic and fracture toughness are investigated. The results show that: (1) Laser rapidly solidified Al₂O ₃/YAG/ZrO₂ ceramic eutectic in situ composite presents a fine interpenetrating network structure, in which Al₂O₃, YAG and ZrO₂ phases are continually interconnected and finely coupled without pores, colonies and grain boundaries between interfaces. (2) Laser scanning rate and power density strongly affect the eutectic growth. With the processing parameters adjusted properly, the eutectic shows homogeneous and coupled lamellar microstructure. The characteristic dimensions of the microstructure are around 2-3 μm for Al₂O₃ and YAG phases, and around 0.2-1 μm for ZrO₂ phases, respectively. (3) The hardness and fracture toughness of the rapidly solidified Al₂O ₃/YAG/ZrO₂ eutectic are 16.7 GPa and 8.0 MPam ^1/2, respectively.