Base Structure Of Alumina Ceramic Material Design And Its Performance Study

Based on the composition design of alumina matrix ceramics, this article proposed a new transient liquid phase sintering process that disperses TiC into alumina in the form of AlTiC. The effect of the content of AlTiC, ZrO₂ and diopside on the performance such as hardness, fracture toughness, bending strength, thermal-shock resistance and friction -wear of the composites was discussed in the paper, and corresponding relationship was erected. New type of alumina matrix ceramic sand blasting nozzle, slab and cellular girder are produced successfully.By doing the job of dispersing TiC into alumina in the form of AlTiC, the physical mechanical performance of the material is improved as the sintering temperature of the material is decreased. The addition of a little ZrO₂ improves the hardness and fracture toughness of the material obviously. A small quantity of diopside can accelerate the composites to be sintered by the way of decreasing the sintering temperature, quickening the process preventing the grains from growing and filling the air hole of the products. Mixed rare earths can accelerate the course of nitriding and improve the properties of the materials.The hardness and fracture toughness of the material reached maximum when AlTiC accounts for 10vol% or 7wt%.The mechanism of AlTiC and zirconia toughening and strengthening alumina is discussed by analyzing microstructure of mixed-powder and sintered body. Part of Al in AlTiC is changed into Al₂O₃ during ball milling, and AlTiC also exists after ball milling. Residual Al is molten at elevated temperature and infiltrates alumina and zirconia. Some molten Al reacts with N₂ and AlN is created, the others vaporize. The addition of AlTiC decreases the sintering temperature, improves toughness of the composites. Al which is separated from AlTiC can make Al₂O₃ slippery. Compared to single alumina, the grain size of Al₂O₃-AlTiC composites is smaller. The addition of AlTiC not only decreases grain size and prevents the grains from growing abnormally, but also impels grains togrow uniformly.Through structural designing, composition and process optimizing, the mechanical properties of alumina matrix ceramics are improved not only in room temperature but also in elevated temperature. Fracture toughness and hardness of sample ATZ2 reached to 8.7 MPa.m1/2 and 23.5Gpa. The hardness of sample ATI is 20GPa and its Fracture toughness is 7.17MPa.m1/2. At the same time the hardness and Fracture toughness of sample ATT1 are separately 21GPa and 7.36MPa.m1/2. As a result, the fracture toughness and hardness of alumina matrix ceramics are all improved obviously.The mechanism and dynamic force of AlTiC to accelerate liquid sintering are investigated by the means of analyzing the shaping and sintering of alumina matrix structural ceramics. Deleterious reaction didn't take place and there is no weak phase in the interface layer during the sintering process. In the process of phase formation, the amount of liquid phase is the main factor that affects dynamic force in the system. The master alloy of AlTiC forms transient liquid phase sintering that enhances hardness and blending strength and produces air hole. Small amount of liquid phase as low content of aluminum in the composite can't wet the matrix fully; high content of aluminum absorbs much heat, which decreases the sintering temperature. The optimal sintering result is reached when the content of AlTiC is about lOvol %.The conception of temperature gradient is introduced into the sintering process, and corresponding mathematics model is set up to ensure the homogeneous contraction of large-scale alumina matrix ceramic products in sintering process. In each temperature interval, the temperature of alumina can be seen as varying equably with time. The functional relation of temperature and time is linear between T, and Ti+i. Materials made in China and the shaping of vacuum grouting is utilized. As the result, the high-performance large-scale alumina products are produced at lower temperature and pressureless sintering.As for AlTiC, diopside and AI2O3 cost less, a lower-cost method of producing high performance alumina matrix structural ceramic products is obtained.