DEVELOPMENTS ON THE MECHANICAL PROPERTIES OF MgO-MgAl2O4 COMPOSITE REFRACTORIES BY ZrSiO4-3 MOL% Y2O3 ADDITION

The effects of additions of ZrSiO4-3 mol% Y2O3 in MgO-MgAl2O4 composite refractories on the mechanical properties and thermal stress resistance parameters were investigated. Significant improvements were achieved in the mechanical properties and R-Rst parameters up to about 2- and 3-fold ratios. The major parameters that were improved were: an increase in the resistance to crack initiation and propagation due to the formation of a Mg2SiO4 phase after the decomposition of zircon; propagation of microcracks formed in the structure by interlinking with each other; arresting or deviation of microcracks when reaching pores or ZrO2 grains released after dissociation of zircon, located together with Y2O3 particles; co-presence of both intergranular and transgranular types of cracks with the incorporation of zircon-Y2O3; an increase in density; and a significant reduction in MgO grain size.