1994 Volume 102 Issue 1183 Pages 225-230
The hot press sintering of ultrafine γ-Al2O3-TiN and θ-Al2O3-TiN composites was studied. Initial materials were prepared by the hydrolysis of ultrafine AlN-TiN composite powder with the followed preheating at 450°C in vacuum and by mixing θ-Al2O3 and TiN powders, all made by the RF plasma chemical synthesis. The hot pressed samples were dense with no observable open porosity. Even when sintered at a temperature as low as 1500°C, the composites exhibited good strength, hardness and fracture toughness. The highest bending strength values were 481±30MPa for the hydrolyzed and 472±60MPa for the mixed composites. Both composites differ by phases content and changes in lattice parameters of α-Al2O3 and TiN. This is due to the different water content in initial aluminas used, γ-Al2O3 and θ-Al2O3, which resulted in different oxidation states of Ti for the mixed and hydrolyzed composites. The enlargement of the Al2O3 and TiN unit cells caused by the dissolution of Ti2O3 and TiO, results in the lattice softening which together with the other characteristics, is an important factor governing the mechanical properties of sintered composites.
