Study On The Graded Joining Of Al₂O₃ And ZrO₂ In Green Bodies

The joining of different ceramics has been a promising and dynamic field since it provides possibility of combining ceramics with different specialties to work in special circumstance which would definitely broaden the application of ceramics. It is a kind of technique which is comparable with the welding in metal area. Although there have been some successful experiments in green state joining of ceramics, there were limited in the area of joining ceramics with similar properties such as thermal expansion coefficients, sintering shrinkage et al. Therefore, joining dissimilar, oxide ceramics with different properties is truly challenging but necessary.Zirconia and Alumina are widely used in many fields because of their good properties. In order to join the two different matrixes together successfully, the slurry was carefully examined to achieve high plasticity which contribute a lot for the modeling and joining in the green state. The experiments showed that the direct joining of Al2O3 and ZrO2 is unsuccessful since the large residual stress induced by the difference of thermal expansion coefficient made the interface or the Al2O3 side near the interface cracked after sintering.In order to reduce the residual stress, three kinds of graded composite are designed to be joined between Al2O3 and ZrO2. It was found that the matrix was joined most successfully with the one which was most similar in component. So we examined the flexural strengths and the interfaces of Al2O3-75Al2O3/25ZrO2, 75Al2O3/25ZrO2-50Al2O3/50ZrO2, 50Al2O3/50ZrO2-25Al2O3/75ZrO2 and 25Al2O3/75ZrO2-ZrO2 (75 and 25 refer to the weight fraction of Al2O3 or ZrO2 in the composite). The flexural strength of each group was satisfactory since it was larger than the weak matrix in the joining. SEM microstructure analysis of interfaces between different joining parts showed that the particles in both interfaces closely inlayed and integrated each other with less deformation, cracks and pores. Therefore, we can join the Al2O3 and ZrO2 if there are some layers of graded composite inserted between them. At last, the influence of the shrinkage of matrix after sintering to the joining was examined.