Al2TiO5-machinable ceramics made by reactive sintering of Al2O3and TiO2

Abstract

Aluminium titanate(Al2TiO5) has extremely anisotropic thermal expansion properties in single crystals, and polycrystalline material spontaneously microcracks in the cooling step after sintering process. These fine intergranular cracks limit the strength of the material, but provide an effective mechanism for absorbing strain energy during thermal shock and preventing catastrophic crack propagation. Furthermore, since machinable BN-ceramics used as an insulating substrate in current micro-electronic industry are very expensive, the development of new low-cost machinable substrate ceramics are consistently required. Therefore, cheap Al2Ti05-machinable ceramics was studied for the replacement of BN ceramics. Al2O 3-Al2TiO5 ceramic composite was fabricated via in-situ reaction sintering. Al2O3 and TiO2 powders were mixed with various mol-ratio and sintered at 1400 to 1600°C for 1 h. Density, hardness and strength of sintered ceramics were systematically measured. Phase analysis and microstructures were observed by XRD and SEM, respectively. Machinability of each specimens was tested by micro-hole machining. The results of research showed that the Al2TiO 5-composites could be used for low-cost machinable ceramics.