电熔MgAl_(2)O_(4)对Al_(2)O_(3)-MgAl_(2)O_(4)复合耐火材料高温蠕变性能的影响

Effect of fused MgAl_(2)O_(4)on high temperature creep properties of Al_(2)O_(3)-MgAl_(2)O_(4) refractory

以烧结板状刚玉和电熔镁铝尖晶石为原料、磷酸为结合剂,在1680℃下制备了刚玉-镁铝尖晶石复合耐火材料样品。在1500℃、0.2 MPa的条件下保温50 h测试试样高温蠕变性能,采用XRD、SEM和EDS分析蠕变前后试样的物相组成及显微结构,分析镁铝尖晶石添加量对刚玉-镁铝尖晶石复合耐火材料高温蠕变性能的影响。结果表明:刚玉-镁铝尖晶石复相材料较纯刚玉材料有着更好的抗蠕变性。镁铝尖晶石骨料在蠕变过程中会与氧化铝基质之间发生固溶反应而在尖晶石颗粒周围形成二次尖晶石层,有效连接了基质与骨料,提高了试样的抗蠕变性。在二次尖晶石层形成的过程中由于Mg;有着更高的迁移速率和在反应界面两侧较高的厚度比,会诱发柯肯达尔效应,导致界面处空位大量积累和孔隙的产生。

The Al_(2)O_(3)bonded MgAl_(2)O_(4)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 MgAl_(2)O_(4)on high temperature creep resistance of Al_(2)O_(3)bonded MgAl_(2)O_(4)fire-resistant composites as well as its mechanism.The results show that Al_(2)O_(3)bonded MgAl_(2)O_(4)fire-resistant composites has better creep resistance than Al_(2)O_(3)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 Mg;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.