Microstructure evolution and model analysis of Al₂O₃/ZrO₂ hypoeutectic ceramic during rapid solidification

Rapid solidification of the super high-temperature Al₂O₃/ZrO₂ melt was studied by a novel method. The melt was prepared by explosion reaction using Al and Zr(NO₃)4 as raw materials and then sprayed to Cu-plate. The heat transfer during the solidification process was analyzed by one-dimensional Finite Element Analysis. The cooling rate of the melt decreased with the increasing distance from the Cu-plate. According to the microstructure evolution, the coating can be divided into four areas: amorphous, nano-crystalline, cellular and dendrite crystal layer. The amorphous and nano-crystalline (50∼100 nm) layers can be obtained at the cooling rate of about 1.687.76 × 10⁵K/s and 0.48∼1.68 × 10⁵K/s, respectively, while the cooling rate of the cellular and dendrite crystal layers were about 0.26∼0.48 × 10⁵K/s and 0.14∼0.26 × 10⁵K/s, respectively. The microstructure of the hypoeutectic ceramics shows that the nano-crystalline, cellular and dendritic crystals of the Al₂O₃ phases were embedded in the Al₂O₃/ZrO₂ eutectic matrix.