Study On The Mechanical Property Of ZrO₂-Al₂O₃ Ceramic Composites

The essential conception and the technigue preparation of ceramic matrix composite are introduced in this thesis, especially making a summary of the characteristics of ZrO₂－Al₂O₃ system composite and its investigation actuality up to date, and it is demonstrated that prominent improvement on the properties of this system materials have been made. However, the composites of excellent properties were prepared with superfine, high pure, uniformly dispersible and active powders by hot-pressing and hot isostatic pressing et al, the cost of the processing would be high and making rigorous demands on the technical process and equipment. In this thesis, the composites are prepared using industrial ZrO₂and Al₂O₃ powders by traditional process. The powders are ball-grinded in order to control the original particle size. The influence of process routing on the sintering behavior, mechanical properties and microstructure are studied, with the purpose of preparing ZrO₂－Al₂O₃ system composite with high performance and low costs. The key of ZrO₂－Al₂O₃ system composite with high performance and low costs made of industrial material is preparing that with appropriate industrial ZrO₂and Al₂O₃ powders. The result of studying the initiative diameter and the grinding effectiveness of different materials showed that the industrial Zircoina G and Alumina A3 powders with high dispersant and activation could be obtained by finable-grinding under the condition of material-ball ratio 1:4 and the time of grinding for 6h and 8h, respectively.It has been demonstrated that ZrO₂－Al₂O₃ system composite with high performance and low costs could be prepared through the optimization of the content of Al₂O₃ and Y2O3 and the processing of ball-grinding and sintering. The results of the research work showed that ZrO₂－Al₂O₃ system composite having high bulk density and mechanical properties could be obtained at the sintering temperature of 1600℃, the heat preservation time of 2 hours by adding 20wt% Al₂O₃ and 3.5mol% Y2O3. And the bending strength and fracture toughness of the composites were 676.7Mpa and 10MPa?m1/2,respectively, which were close to those of composites made of ZrO₂ and Al₂O₃ powders synthesized by wet chemical approach. The phase composition of sintered bodies were analyzed by XRD. The results indicated that there were only ZrO₂ and Al₂O₃ phases in sintered bodies. The content of monoclinic ZrO₂ decreased gradually with the increasing content of stabilizer Y2O3. But the content of cubic phase increased and the content of metastable tetragonal phase, which associated with the stress-induced transformation decreased when excessive Y2O3 was added, resulted in the mechanical properties of composites decreasing. And the mechanical properties of composites were preferable by adding 3.5mol%Y2O3. The content of monoclinic ZrO₂ were least with 20wt% Al₂O₃ in the composites, which was 32% of the total content of ZrO₂ approximately. The results revealed that the grain growth of ZrO₂ was inhibited with the introduction of Al₂O₃properly in the ZrO₂ matrix ceramic which was in favor of leaving large amount of metastable tetragonal ZrO₂ in the body and resulted in higher effect of transformation. The microstructure of ZrO₂－Al₂O₃ system composite were investigated by SEM. The results revealed that the particle diameters of ZrO₂ were larger relatively by adding 0 and 10wt% Al₂O₃ , which were 1～2um and 1.5～2um respectively; There were large amount of pores whose diameters were 8¹0um and the composites were disinterred obviously with 40wt% Al₂O₃. The grain growth of Al₂O₃ was favorable and there were no pores and disfigurement visibly in the bodies by adding 20wt% Al₂O₃. The particle diameters of ZrO₂ were finer relatively, which were 1¹.5um, and large portion of that were less than 1um, and Al₂O₃ dispersed in the ZrO₂ matrix ceramic uniformly with 3⁵um particle diameters. The results revealed that not only the grain growth of ZrO₂ was inhibited with the introduct...