Design And Preparation Of The Al₂TiO₅/Al₂O₃ Composite Ceramic And FGM

Aluminium Titanate (AT) has many excellent properties such as low thermal expansion coefficient, thermal conduction coefficient, high melting point, endured corrosion and thermal resistance, so it is one of the best materials with low thermal expansion coefficient resisting high temperature. But it also includes two fatal disadvantages: first, AT is difficult to be sintered and its density is low , which causes its lower strength; second, In the temperature range of 1023-15 73 K, AT can decompose into Al2O3 and TiO2 easily, which can cause the stress concentrated and raise the heat expansion rate. In this dissertation, MgO5 is introduced to form solid solution to restrain the decomposition of AT in high temperature. Then AT is mixed with the Al2O3, forming gradient composite to raise the integral intensity of the material and not affecting the thermal properties.The experimental results show that the additive MgO5 can effectively restrain the decomposition of AT and promote the sinter process, which enhances the density of AT. When the content of MgTiaO5 is 10mol% and the composite is kept at the 1100 for lOh, the decomposition rate of AT is far below 9%; the density of sintered material at 1500 with additive M2T is about 10 percent higher than that of those without any additives. If appropriate M2T is introduced, the composite can also obtain fine thermal properties. When the content of M2T is 10mol%, the thermal expansion coefficient is -0.45x10-6/. Through investigating the sinter process of Al2O3 and AT composite, the sinter parameters of ATiO5/ Al2O3 is obtained. Based on the study of the AbTiO5/ Al2O3 composite, the finite element method is use to relax residual thermal stresses and design the structure. The outcome indicates that the graded composite can effectively reduce the residual thermal stress. When the distribution p is 1.2, the relaxation effect is most conspicuous and up to 60%. Finally, the ATiO5/ Al2O3 functionally graded material is fabricated by the power stacking-method based on the fabrication technique and structure design discussed above.