TiN/AI_2O_3 Functionally Graded Material Fabricated by In-situ Reaction

摘要

TiN/Al_2O_3 functionally graded composite was fabricated by in-situ aluminothermic reduction of TiO_2 in coke bed from mixtures of TiO_2 powder and metal Al powder. The reaction process, phase composition, and microstructure of sample treated at 1500℃ for 3h were analyzed by XRD, SEM and EPMA. The results indicated that the thermite reduction of TiO_2 involves several transitional stages and its initial reaction temperature is lowered by prior reaction between Al and TiO_2. EPMA analysis showed that the TiN/Al_O_3 ratio in TiN/Al_2O_3 functionally graded material products changes gradually across the samples without distinct interface between the different layers. The microstructure of the composite changes gradually, and the size of TiN grains increases from the verge region of samples to the centre of samples. These results above were in agreement with thermodynamic analysis.