Al粉和Si粉对铬刚玉质材料显微结构的影响

Influences of Al and Si powders on microstructure of chrome-corundum material

以w(Al2O3)=99.48%的板状刚玉细粉和颗粒料(粒度为5～3、3～1和≤1 mm)、w(Al2O3)=99.15%的α-Al2O3微粉、w(Cr2O3)=99.62%的Cr2O3微粉为主要原料,研究了在氧化气氛下1 500℃保温3 h处理后Al粉(加入量(w)分别为3%、6%、9%、12%、15%)和Si粉(加入量(w)为3%)复合加入时对铬刚玉质材料显微结构的影响。结果表明:经过1 500℃保温3 h处理后,Al粉和Si粉的引入改变了材料的结构,使材料的边缘部位结构致密,中心部位结构疏松。在试样表层,Si氧化生成SiO2,SiO2与Al2O3反应生成莫来石,产生体积膨胀,封闭了材料表面的气孔;同时,Al粉原位反应生成了活性较大的Al2O3,并与Cr2O3反应生成铝铬固溶体,使材料烧结更致密,阻止了O2的进入,使材料内部缺氧,于是材料中心部位的Al、Si不能被氧化,Al把Cr2O3中的Cr置换出来,一部分Cr与Si生成金属间化合物Cr5Si3,另一部分则以单质Cr的形态存在于材料中。

The influence of aluminum powder （3wt%,6 wt%,9 wt%,12 wt% and 15 wt%,respectively） combined with silicon powder （3wt%） on the microstructure of chrome -corundum material after being fired at 1500℃ for 3 h in oxidation atmosphere was studied using tabular corundum powder and coarse grains （w（Al2O3） =99.48%,5-3,3-1 and ≤1 mm）,α-Al2O3 （w（Al2O3） =99： 15%） and Cr2O3 powder （w（Cr2O3） =99.62%） as main starting materials：The result showed that addition of the mixed powder changed the material＇ s structure：the edge area of the specimens became dense while the core part became loose. On the surface of the specimen,generated SiO2 reacted with Al2O3 and formed mullite,which led to volume expansion and closed the open pores. Meanwhile, active alumina formed by in-situ reaction of metal Al and then reacted with Cr2O3 forming alumina-chrome solid solution,which densified the material and blocked the entry of oxygen, making aluminum and silicon in the central part couldn＇t be oxidized. Chromium was replaced from Cr2O3 by metallic aluminum. Part of the chromium reacted with silicon and formed intermetallic compound Cr5Si3 ,while the rest part existed in the form of elementary chromium.