Abstract:

The hot modulus of rupture,the creep resistance and the microstructure of high purity sintered MgAl₂O₄ materials with 66%,71%,75%,85%,and 90% Al₂O₃ (by mass) and fused-rebonded MgAl₂O₄ materials with varying Al₂O₃ contents were studied.The results show that:(1)for high purity sintered MgAl₂O₄ materials,the hot modulus of rupture increases along with the increase of the Al₂O₃ content;the sample with 66 mass% Al₂O₃ is spinel-periclase composites in which the existence of periclase weakens the bonding force of grain boundaries,thus resulting in low hot strength;for the samples with 71%,75%,and 85% Al₂O₃,with the increase of the Al₂O₃ content,the grain size increases,and the bonding strength of grain boundaries increases,the main fracture mode changes from intergranular fracture to transgranular fracture,and the hot strength also increases;the sample with 90% Al₂O₃ is spinel-corundum composite which leads to lower hot strength than that of the sample with 85% Al₂O₃;(2)the sinterability of the fused-rebonded MgAl₂O₄ materials decreases with the increase of the Al₂O₃ content,while the creep resistance increases.

Key words: magnesium aluminate spinel, non-stiochiometry, hot modulus of rupture, creep resistance

摘要：

研究了Al₂O₃含量(w)分别为66%、71%、75%、85%、90%的高纯烧结镁铝尖晶石材料和不同Al₂O₃含量的电熔再结合镁铝尖晶石材料的热态抗折强度、压蠕变特性、显微结构等。结果表明:1)对于高纯烧结镁铝尖晶石材料,随着Al₂O₃含量的增大,其热态抗折强度都有所增大。Al₂O₃含量为66%(w)的试样是尖晶石-方镁石复相材料,方镁石的存在弱化了晶界结合力,高温强度较小。Al₂O₃含量(w)分别为71%、75%、85%的试样,随着Al₂O₃含量的增大,晶粒尺寸变大,晶界结合力增强,断裂方式由沿晶断裂为主过渡到穿晶断裂为主,高温强度也随之增大。Al₂O₃含量为90%(w)的试样为尖晶石-刚玉复相材料,导致其高温强度低于Al₂O₃含量为85%(w)的试样的。2)电熔再结合镁铝尖晶石试样的烧结性随着Al₂O₃含量的增加而减小,抗蠕变性随着Al₂O₃含量的增加而增大。

关键词: 镁铝尖晶石, 非化学计量, 热态抗折强度, 抗蠕变性