Developments on the mechanical properties of MgO–MgAl2O4 composite refractories by ZrSiO4–3 mol% Y2O3 addition

Improvements and the effects of additions of ZrSiO4–3 mol% Y2O3 into MgO–MgAl2O4 composite refractories on mechanical properties and thermal stress resistance parameters were investigated. Significant improvements were achieved on mechanical properties and R–Rst parameters up to ∼2 and ∼3-fold ratios. The major parameters improving mechanical properties and thermal behaviour of refractories were determined as follows: (i) the increase in resistance to crack initiation and propagation due to formation of Mg2SiO4 phase after decomposition of zircon; (ii) propagation of the microcracks formed in the structure for a short distance by interlinking each other; (iii) arresting or deviation of microcracks when reaching pores or ZrO2 grains released after dissociation of zircon, located together with Y2O3 particles, and furthermore; (iv) co-presence of both intergranular and transgranular types of cracks, and with incorporation of zircon–Y2O3; (v) increase in density; and (vi) a significant reduction in MgO grain size.