Fracture behavior and thermal shock resistance of alumina-spinel castables-Effect of added fused zirconia-alumina

Abstract This study aims to clarify the influence of fused zirconia-alumina (FZA) on the fracture behavior and thermal shock resistance (TSR) of alumina-spinel castables, and discover the relationship between toughness parameters and TSR. Alumina-spinel castables with different FZA contents (0, 2, 4, 6, 8, and 10 wt.%) were prepared using tabular alumina, fused spinel, calcium aluminate cement, ultrafine alumina powder, and FZA as raw materials. The fracture behavior and TSR of alumina-spinel castables were determined by a wedge splitting test (WST) and a water quenching test, respectively. The results show that the flexibility of alumina-spinel castables can be significantly enhanced by introducing FZA. With increasing FZA content, the load-displacement curves change from typical brittle fracture behavior to non-linear fracture behavior. The flexibility parameter (ratio of GF/σNT) of the castables increases from 8.3 μm to 13.6 μm when FZA content increases from 0 wt.% to 10 wt.%. The flexibility improvement of castables containing FZA can be attributed to the formation of microcracks caused by the transformation of ZrO2. The TSR of alumina-spinel castables can also be significantly improved by adding FZA. The ratio of residual cold modulus of rupture (CMOR) of the castables increases from 12.3% to 34.2% when FZA content increases from 0 wt.% to 10 wt.%. The improvement in TSR can be attributed to a decrease in the stored elastic energy and a subsequent increase in the specific fracture energy of the castables. Generally, alumina-spinel castables with non-linear fracture behavior have good thermal shock resistance. There is a significant correlation between the flexibility parameter (GF/σNT ratio) and the ratio of residual CMOR; the correlation coefficient is 0.96.