Abstract: Bauxite-based homogenized grogs with 85 mass% Al₂O₃ were prepared through wet co-grinding homogenization and high-temperature heat treatment,and utilizing D-K type bauxite as the raw material.The evolution of the phase composition,microstructure,and properties of the bauxite-based homogenized grogs during the heating process (800-1 630 ℃) was systematically studied using thermodynamic software FactSage,XRD and SEM.The results show that the main crystal phases of the sample are corundum and mullite;as the heat treatment temperature increases,the corundum content decreases gradually while the mullite content increases gradually;(2)within 800-1 550 ℃,as the heat treatment temperature increases,the apparent porosity and water absorption of the sample rapidly decrease,while the linear shrinkage,bulk density,and the cold compressive strength significantly increase;within 1 550-1 630 ℃,the properties of the sample tend to stabilize,with the apparent porosity less than 3.4%,the water absorption rate less than 1.00%,the linear shrinkage rate of about 16%,the bulk density higher than 3.27 g·cm^-3,and the cold compressive strength higher than 460 MPa;the sample is basically densified;(3)after heat treatment at temperatures of 1 400 ℃ or below,the corundum crystals in the sample are small and porous,while the mullite crystals are microcrystalline and not fully developed;the pores are mainly open or through;after the heat treatment at 1 600 ℃ or above,the sample exhibits a typical network structure of alternating corundum and mullite phases;the glass phases are few and isolatedly distributed in the network structure of the corundum grains or mullite grains;the pores are mainly closed;(4)thermodynamic calculations show that the liquid phase is generated in the samples at 1 150 ℃,and the amount of the liquid phase gradually increases with the increasing temperature;while the viscosity of the hot liquid phase significantly decreases.

Key words: bauxite-based homogenized grogs, heat treatment temperature, phase composition, microstructure

摘要： 以D-K型铝土矿为原料,采用湿法共磨均化、高温热处理工艺制备了Al₂O₃含量为85%(w)的矾土均化料,采用热力学软件FactSage、X射线衍射仪、扫描电子显微镜等手段系统研究了矾土均化料中物相组成、显微结构以及性能在受热过程中(800~1 630 ℃)的演变。结果表明:1)试样的主晶相为刚玉和莫来石,随着热处理温度的升高,试样中刚玉相含量逐渐减少,莫来石相的含量则逐渐增多。2)当热处理温度在800~1 550 ℃升高时,试样的显气孔率和吸水率快速下降,线收缩率、体积密度和常温耐压强度显著增大;当热处理温度在 1 550~1 630 ℃时,试样的各项性能趋于稳定,显气孔率小于3.4%,吸水率小于1.00％,线收缩率约16%,体积密度大于3.27 g·cm^-3,常温耐压强度大于460 MPa,试样基本实现致密化。3)在1 400 ℃及以下温度热处理后,试样中刚玉晶体粒径较小且呈多孔状,莫来石晶体呈微晶态,尚未发育完全,气孔以开口或贯通气孔为主;在1 600 ℃及以上温度热处理后,试样呈典型的刚玉和莫来石两相穿插网络结构,玻璃相数量少且孤立分布在刚玉晶粒间或莫来石晶粒构成的网络结构中,气孔以封闭气孔为主。4)热力学计算表明,试样在1 150 ℃开始出现液相,随着温度的升高,试样的液相量逐渐增大;而高温液相的黏度则显著降低。

关键词: 矾土均化料, 热处理温度, 物相组成, 显微结构