Volume 113 (2005) Issue 1314 Pages 185-187
In order to fabricate machinable spinel/mica composite, 40 mass% mica-composition (KMg3AlSi3O10F2) glass powder was mixed with magnesia and alumina powders and the powder mixture was sintered. Furthermore, in order to improve the mechanical properties of the composite, silicon carbide was added to the powder mixture. The densification and the microstructure development of spinel/mica composite progressed drastically at 1150-1200°C. The dense machinable spinel/mica composite of which relative density was about 99% was obtained at 1200°C. The machinability was caused by the interlocking microstructure of mica crystals. The addition of silicon carbide retarded the densification and the grain growth of spinel and mica. However, the sintered composite also showed machinability and the fracture toughness and hardness were enhanced by the silicon carbide. Though the sintered composite was not densified sufficiently by the addition of silicon carbide, the finer microstructure caused a little improvement of the bending strength.