Fabrication, Thermal Shock-resistance And Aluminizing-resistance Of Al₂TiO₅/Al₂O₃ Composites

Aluminium Titanate ceramic is one of the best materials with low thermal expansion coefficient, low thermal conduction coefficient, high melting point, endured corrosion and thermal shock-resistance. For the sake of two disadvantages of Al2TiO5 that its strength is low, and that in the middle temperature range it can decompose into Al2O3 and TiO2 easily. In this dissertation, Magnesium Titanate and Ferric Titanate are introduced to form solid solution to restrain the decomposition. Al2TiO5/Al2O3 composites are fabricated to offer not only improved strength but also excellent thermal shock-resistance.The experimental results show that the additive MgTi2O5 and Fe2TiO5 can effectively restrain the decomposition of Al2TiO5 and promote the sintering process, which enhances the density of Al2TiO5. Aluminium Titanate becomes more and more stable in the middle temperature range with the content increase of the additive. Aluminium Titanate with 10mol% MgTi2O5 ,4mol% Fe2TiO5 or mixed additive 5mol% MgTi2O5& 1mol% Fe2TiO5 doesn't'decompose after being kept at 1100℃ for 50 hours.Density, strength, elastic modulus and thermal expansion coefficient of the Al2TiO5/Al2O3 composites become larger with the content increase of Al2O3, but the thermal shock-resistance decreases. The Al2TiO5-40V%Al2O3 composites show the best general performance. After sintered at 1450 ℃ for 2 hours, the relative density ,strength, thermal expansion coefficient of the Al2TiO5-40Vol%Al2O3 composites reach 95.4%,43.2Mpa, 1.097 × 10-6/℃ respectively. After 5 times thermal shock at 700 ℃, its microstructure still retains and its residual strength is 71.4% of the original strength. Though Al2TiO5-90Vol%Al2O3 composites have high density and high strength (272.1MPa),its residual strength is only 19.3% of its original strength after 5 time thermal shock at 700 ℃.After the Al2TiO5/Al2O3 composites being soaked in liquid aluminium for 100hours, liquid aluminium penetrates into the composites along the crack as a result of thermal shock when the content of Al2TiO5 is less than 20Vol%, but there is no aluminium in the composites when the content of Al2TiO5 is larger than 40Vol%.