Effect of the cooling rate of the eutectics of Al2O3-ZrO2 system on the stability of phase constituents

Effect of the cooling rate of the melt on stability of phase constituents of eutectics of Al2O3-ZrO2 system has been studied. A state diagram of Al2O3-ZrO2 system is refined. Peculiarities of phase transformations of specimens of the eutectic composition after melting, quenching, vibrogrinding and heat treatment have been investigated. As a result of quenching metastable phases - ZrO2cub and γ-Al2O3, appear; defectness of the crystal structure of oxides increases. In melting and quenching of pure corundum metastable modifications are not formed, increase of defects of crystals melted corundum in comparison with the annealed one is not observed. After heat treatment of specimens of the eutectic composition metastable cubic zirconium dioxide content decreases, and γ-Al2O3 disappears. Vibrogrinding decreases also the content of metastable phases; the more is the period of vibrogrinding, the higher is the ZrO2 content of the monoclinic form. Metastable modifications ZrO2 and Al2O3 are not detected during investigations of eutectic specimens including stabilized ZrO2cub