Al_2O_3-ZrO_2-SiO_2系相图结构特征的研究

STUDY ON STRUCTURAL FEATURE OF PHASE DIAGRAM FOR Al_2O_3-ZrO_2-SiO_2 SYSTEM

按照Al_2O_3/SiO_2比值,在Cevales给出的Al_2O_3-ZrO_2-3Al_2O_3·2SiO_2系的无变量点附近选择了6个组成,对其进行了熔体自然冷却、缓冷和淬冷析晶试验,并对析晶后的试样进行了XRD、SEM和EDAX分析,结果表明:(1)相平衡关系与Cevales给出的Al_2O_3-ZrO_2-3Al_2O_3·2SiO_2系相图的结构特征吻合得很好,其无变量点为低共熔点;(2)莫来石晶相的Al_2O_3/SiO_2比值波动于A_3S_2-A_(?-7)S之间,与Aramaki和Roy测定的Al_2O_3-SiO_2系莫来石稳态固溶体的Al_2O_3上限含量为74.3％是一致的;(3)析晶的单一莫来石晶相的EDAX能谱中不存在Zr谱线,ZrO_2在莫来石中的固溶问题,应进一步研究。

According to the difference of Al_2O_3/SiO_2 ratios, around invariant point of Cevales' Al_2O_3-ZrO_2-3Al_2O_3·2SiO_2 system, six different compositions Were selected and put into experiments involving crystallization of melts in natural and slowly-controlled cooling and quenching conditions respectively. The phase components and compositions of the crystallized specimens were studied by use of XRD, SEM and EDAX. The results indicate that(1) the equilibrium phase relationship is in good agreement with the structure feature of phase diagram of Al_2O_3-ZrO_2-3Al_2O_3·2SiO_2 system established by Cevales,and the ternary invariant point is eutectic point; (2)the stable solid solution range of mullite is from A-3S_2 to A-(1.7)S, which coincided with the Al_2O_3 upper limit of 74.3％ givin by Aramaki and Roy for the stable mullite solid solution in Al_2O_3-SiO_2 system;(3)the EDAX spectra obtained show no Zr specific line for the single-phase mnllite crystallized from the melts. So problem of the solid solution of ZrO_2 in mullite would require further investigations.