Developments on the mechanical properties of MgO-MgAl_2O_4 composite refractories by ZrSiO_4-3 mol% Y_2O_3 addition

摘要

Improvements and the effects of additions of ZrSiO_4-3 mol% Y_2O_3 into MgO-MgAl_2O_4 composite refractories on mechanical properties and thermal stress resistance parameters were investigated. Significant improvements were achieved on mechanical properties and R-R_(st) 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 Mg_2SiO_4 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 ZrO_2 grains released after dissociation of zircon, located together with Y_2O_3 particles, and furthermore;;(iv) co-presence of both intergranular and transgranular types of cracks, and with incorporation of zircon-Y_2O_3;;(v) increase in density;;and (vi) a significant reduction in MgO grain size.