Microstructural features of alumina refractories with mullite-zirconia aggregates

摘要

Refractory materials are often subjected to high temperatures and loads and their performance depends on their microstructural evolution during use. In this context, microstructural changes were monitored in alumina-based refractories containing mullite zirconia aggregates and heat-treated at 1400 deg C and 1500 deg C for 2, 6, and 18 days. With the purpose of inducing in situ mullite formation, bricks containing microsilica were also prepared and heat-treated at 1500 deg C for 6 days for the sake of comparison. These heat treatments allowed for an evaluation of the use of refractories from the standpoint of temperature and time In this work, scanning electron microscopy and X-ray diffraction analyses were made to identify the phases in the materials. The Rietveld method was also used for quantitative phase analyses. Interfacial reactions occurred between alumina and aggregates and between alumina and microsilica, causing the system to become mullitized. The effect of in situ-formed mullite was particularly evident in the results of the modulus of rupture of the materials containing microsilica. Creep tests revealed a reduction in the creep rate of materials treated at 1500 deg C for 18 days.