PHASE-EQUILIBRIA, MICROSTRUCTURE AND PROPERTIES OF SOME MGO-AL2O3 REFRACTORIES

Four MgO-Al2O3 batches were processed from precipitated magnesium and aluminium hydroxides with weight ratios of 100/0 (MA1), 72/28 (MA2), 3 2168 (MA3), and 0/100 (MA4). These batches were fired using a two stag e firing process up to 1600-1700-degrees-C in order to study their pha se equilibria and microstructures. The phase equilibria data were calc ulated from the available phase diagrams and the microstructures exami ned using an electron probe microanalyser. Densification parameters as well as the load bearing capacity of fired pellets were assessed in r elation to their phase equilibria and microstructures. It is concluded that dense and highly refractory spinel and corundum grains could be prepared by firing at two stages up to 1600-degrees-C from MA3 and MA4 , respectively, but firing up to 1700-degrees-C was required to produc e dense and highly refractory periclase and spinel-bonded periclase gr ains from MA1 and MA2, respectively. However, controlled additions of suitable dopant cations were required to inhibit discontinuous grain g rowth of corundum, spinel, and/or periclase phases to facilitate the a chievement of maximum bulk density of the fired MgO-Al2O3 grains. (C) 1993 The Institute of Materials.