刚玉骨料种类与粒度对刚玉-莫来石材料抗热震性的影响

Effects of kind and grain size of corundum aggregate on thermal shock resistance of corundum-mullite materials

以莫来石和电熔白刚玉或板状刚玉为骨料,氧化铝粉、氧化硅粉、红柱石粉为基质料,纸浆为结合剂,同时以≤0.15 mm(100目)的刚玉细骨料取代较粗(1～0.15 mm或0.5～0.15 mm)的刚玉骨料,制备了2个系列、不同粒度级配的刚玉-莫来石试样,并分别以抗折强度保持率和弹性模量保持率为评价指标,研究了刚玉骨料种类和粒度对刚玉-莫来石材料性能的影响。结果表明:1)分别以白刚玉和板状刚玉为骨料时,刚玉-莫来石材料热震后的弹性模量保持率与抗折强度保持率并不完全一致;2)以≤0.15 mm骨料代替较粗骨料,虽能提高材料强度,但可能会降低其抗热震性能。分析认为:刚玉-莫来石材料抗临界危险裂纹扩展能力与材料热震强度保持率一致,相对于弹性模量保持率,以强度保持率作为此类材料抗热震性的评价标准更为合适;由于板状刚玉骨料周围残余应力的存在,热震实验后以板状刚玉为骨料的刚玉-莫来石材料具有更高的抗折强度保持率。

Two series of corundum -mullite specimens with different grain size distributions were prepared using mullite,white fused corundum or tabular corundum as aggregates,alumina powder, silica powder, andalusite powder as matrix,with corundum fine aggregate （ ≤0.15 mm） replacing corundum coarse aggregate （1 - 0.15 mm or 0.5 -0.15 mm）. Using the retention ratios of cold rupture modulus and elastic modulus as evaluatingcriteria respectively,the effects of kind and grain size of corundum aggregate on thermal shock resistance of corundum -mullite materials were studied. The results show that there exists some inconsist- ency for the retained ratios of elastic modulus and cold rupture modulus after thermal shock for corundum -mullite specimens with different aggregates; and replacing some coarse corundum aggregate with ≤0. 1.5 mm fine corundum aggregate results in high strength,but declines thermal shock resistance. It was considered that the retention ratio of cold rupture modulus not of elastic modulus after spalling is cor^sistent with the resistance to the propagation of critical crack, so it is a more appropriate criterion for thermal shock resistance of corundum -mullite materials. In addition, corundum -mullite materials with tabular alumina as aggregate have better thermal shock resistance because of the residual stress around the aggregate.