Crystallographic texture on high zirconia refractories
Résumé
New compositions of refractory materials with a very high content of zirconia are being developed for the processing of special glasses. The use of these refractories requires good control of the manufacturing process to avoid critical flaws due to severe thermo-mechanical stresses. These materials exhibit a microstructure containing monoclinic zirconia dendrites embedded into a glassy phase.
The purpose of this study is to characterize the coupling between the microstructural texture and the cooling process of high zirconia refractories. The cooling stage creates an important thermal gradient between the core and the skin of the block. During this cooling process, zirconia crystallizes under the cubic (C) phase and then two phase transitions occur (cubic to tetragonal (T) and tetragonal to monoclinic (M)), which can influence the macroscopic mechanical properties. Neutron diffraction experiments have been performed, on samples from solidified blocks to evaluate the relationship between the thermal gradient of cooling and the crystallographic texture. It was shown that the stress field created during the cooling process manages the preferential orientation of zirconia crystals.