Acoustic characterization and microstructure of high zirconia electrofused refractories

A new line of electrofused refractory materials with a very high content of zirconia (HZ) has been developed to satisfy the needs of new generation manufacturing glass furnaces. Such materials are subjected to severe operating conditions (temperature and corrosion) during their manufacturing and service life. These HZ materials required very high temperature casting and a suitable annealing process to prevent defects and cracks during manufacturing. Therefore, a research program has been launched to build numerical tools able to predict the thermo-mechanical behaviour of these materials during one of the most critical phases of manufacturing: the controlled cooling of the refractory blocks after melting and casting. The efficient development of such a tool requires the knowledge of thermo-mechanical properties of these materials with temperature, in conditions close to that occurring during processing. In the framework of this approach, the present paper deals with the characterization of elastic properties of two HZ materials, using two mechanical testing devices i.e. a pulse echography technique and a tensile test device. An innovative acoustic emission device is also used to help in identification of microdamage occurrence. The goal of this study is to investigate the microstructure organisation of materials at very fine scale (<100 mu m) in order to correlate the obtained results with the macroscopic properties of the material. Characterisations are also performed at intermediate temperature to establish correlations with the manufacturing process. (C) 2009 Elsevier Ltd. All rights reserved.