Effect of fused MgAl₂O₄ on high temperature creep properties of Al₂O₃-MgAl₂O₄ refractory

The Al₂O₃ bonded MgAl₂O₄ fire-resistant composites were prepared with tabular alumina and fused magnesia-alumina spinel as raw materials, and phosphoric acid as binder and then sintered at 1680℃. The creep resistance test was conducted at 1500℃ under 0.2 MPa with insulation for 50 h, The specimens after creep resistance test were characterized and analyzed by XRD, SEM and EDS to investigate the effect of adding amount of MgAl₂O₄ on high temperature creep resistance of Al₂O₃ bonded MgAl₂O₄ fire-resistant composites as well as its mechanism. The results show that Al₂O₃ bonded MgAl₂O₄ fire-resistant composites has better creep resistance than Al₂O₃ composite. During the creep test, magnesium-aluminum spinel aggregate will react with alumina matrix to form secondary spinel layer around the spinel particles, which effectively connects the matrix and aggregate and improves the creep resistance of the specimens. During the formation of the secondary spinel layer, due to the higher migration rate of Mg²⁺ and the higher thickness ratio on both sides of the reaction interface, the Kirkendall effect will be induced, resulting in a large number of vacancies and pores at the interface.