Insights into high thermal stability of laser additively manufactured Al2O3/GdAlO3/ZrO2 eutectic ceramics under high temperatures

Abstract

Laser additive manufacturing techniques have been considered to be the most promising methods to fabricate melt-grown Al 2 O 3 -based eutectic ceramics which are potential candidates for high temperature structural applications. In this paper, Al 2 O 3 /GdAlO 3 /ZrO 2 ternary eutectic ceramic was additively manufactured based on one-step melt-growth by laser directed energy deposition, and its thermal stability under high temperatures was studied. The results indicate that the as-solidified eutectic composite consists of ultrafine phases of α-Al 2 O 3 , GdAlO 3 and t-ZrO 2 , and presents an irregular eutectic morphology with amounts of terminations and branches. The 3D-printed eutectic ceramic exhibits a superior thermal stability that no mass variation and no phase transition occur even after annealed at 1500 °C for 200 h. In addition, the submicron-scaled eutectic microstructure and the polished surface topography can maintain stability up to 1400 °C which is higher than 80% of its melting point (>0.8 T m ). With further increasing the temperature, obvious microstructure coarsening, and surface holes formation occur, leading to the severely deterioration of the mechanical property. The hardness of the as-deposited eutectic ceramic rapidly decreases from 15.84 ± 0.61 GPa to 13.01 ± 0.40 GPa after 200 h annealed at 1500 °C. The results indicate that the additively manufactured Al 2 O 3 -based eutectic ceramics have great potential to be long-time high-temperature structural materials applied at elevated temperatures. • Highly dense Al 2 O 3 /GdAlO 3 /ZrO 2 eutectic ceramic is 3D-printed based on melt growth. • Thermal stability of the additively manufactured eutectic ceramic is studied under high temperatures. • Critical transition temperature from stability to instability is determined, and the instability mechanism is revealed.